Issued  October  26,  1910. 

U.  S.  DEPARTMENT  OF  AGRICULTURE. 


FARMERS’  BULLETIN  410. 


POTATO  CULLS  AS  A  SOURCE  OF 
INDUSTRIAL  ALCOHOL; 

WITH  A  GENERAL  DISCUSSION  OF 
THE  AVAILABILITY  OF 
OTHER  WASTES. 


BY 


A.  O.  WENTE, 

Fermentation  Expert, 

AND 

.  L.  M.  TOLMAN, 

Chief,  Washington  Food  Inspection  Laboratory. 


WASHINGTON: 

GOVERNMENT  PRINTING  OFFICE, 

1910, 


LETTER  OF  TRANSMITTAL. 


U.  S.  Department  of  Agriculture, 

Bureau  of  Chemistry, 
Washington ,  D.  C.,  May  23,  1910. 

Sir:  I  have  the  honor  to  submit  to  you  for  approval  a  report  which 
is  intended  to  reply  to  the  numerous  requests  for  practical  informa¬ 
tion  both  as  regards  the  apparatus  and  the  methods  employed  in  the 
manufacture  of  denatured  alcohol  from  farm  waste  materials.  The 
description  of  methods  and  apparatus  for  the  utilization  of  waste 
potatoes  or  culls  is  given  in  detail  and  from  this  may  be  obtained 
sufficient  data  to  enable  one  to  handle  various  other  cheap  or  waste 
materials.  As  the  information  contained  herein  is  of  particular 
interest  to  agricultural  communities,,  I  recommend  that  it  be  pub¬ 
lished  as  a  Farmers’  Bulletin. 

Respectfully, 

H.  W.  Wiley, 

Chief,  Bureau  of  Chemistry. 

Hon.  James  Wilson, 

Secretary  of  Agriculture. 

2 

410 


CONTENTS. 


Page. 

Introduction . 5 

Purpose  of  bulletin .  5 

Source  of  alcohol .  5 

Nature  and  use  of  denatured  alcohol .  5 

Conditions  necessary  for  successful  alcohol  production .  6 

Special  availability  of  potatoes .  6 

Fundamental  considerations  in  establishing  a  potato  distillery .  7 

Location .  7 

Machinery  and  equipment .  7 

Control  of  operation .  8 

Estimated  costs  of  a  potato  distillery .  9 

Cost  of  plant .  9 

Cost  of  operation .  9 

Value  of  output .  10 

Government  regulations .  10 

Details  of  operating  a  potato  distillery .  11 

Preparation  of  the  mash .  11 

Fermenting  the  mash .  13 

Determination  of  the  gravity  and  acidity  of  the  fermented  mash .  15 

Distilling  the  alcohol .  16 

Denaturing  the  alcohol .  18 

Yield  of  alcohol .  18 

Malt .  19 

Diastatic  power  of  malt .  19 

Preparation  of  green  barley  malt .  19 

Steeping  the  grain .  19 

Sprouting  the  grain .  20 

Crushing  the  green  malt .  21 

Preparation  and  value  of  green  malt  from  various  grains .  22 

Relative  value  of  green  and  dried  malt .  23 

Yeast .  24 

Development  of  yeast .  24 

Spontaneous  and  pure  culture  yeasts .  24 

Development  of  a  start  yeast .  25 

Preparation  of  a  spontaneous  hop  yeast .  25 

Yeast  mashes .  25 

Preparation  of  a  grain  yeast  mash .  26 

Preparation  of  a  potato  yeast  mash .  27 

Analytical  data .  32 

Composition  of  the  whole  potatoes .  32 

Purchase  on  basis  of  starch  content . — .  32 

Simple  method  of  determining  starch .  33 

Analysis  of  potato  skins .  33 

Composition  of  the  potato  slop .  34 


410 


3 


4 


CONTENTS. 


Page. 

Slop  feeding .  34 

General  discussion .  34 

Comparison  of  grain  and  potato  slops .  35 

Coefficients  of  digestibility . , . . .  37 

Production  values . • .  38 

Nutritive  ratio .  38 

Rations  containing  slop .  39 


ILLUSTRATIONS. 


Page. 

Fig.  1.  Mashing  and  fermenting  apparatus  for  potato  distillery .  12 

2.  Apparatus  for  determining  the  specific  gravity  of  a  mash .  13 

3.  Apparatus  for  determining  the  acidity  of  a  mash .  14 

4.  Distilling  apparatus . , .  17 

5.  Apparatus  for  determining  the  starch  content  of  potatoes .  18 

6.  Barley  steeping  tank .  20 

7.  A  sprouting  grain  of  barley  at  different  stages  of  development .  21 

8.  Green  malt  crusher .  22 

9.  Development  of  a  yeast  cell .  24 

10.  Growth  of  yeast  in  a  liquid  containing  sugar  as  seen  under  the  micro¬ 
scope .  25 


410 


POTATO  CULLS  AS  A  SOURCE  OF 
INDUSTRIAL  ALCOHOL. 


INTRODUCTION. 

PURPOSE  OF  BULLETIN. 

This  bulletin  has  been  prepared  with  two  purposes  in  view:  First, 
to  outline  the  conditions  which  must  be  considered  before  attempting 
to  make  denatured  alcohol,  and,  second,  to  give  in  detail  the  practical 
methods  for  the  manufacture  of  alcohol  from  potatoes.  A  discussion 
of  general  conditions  is  given  in  order  to  answer  the  many  inquiries 
received  at  the  Department  as  to  the  availability  of  various  materials 
and  it  is  hoped  that  persons  interested,  by  a  careful  reading  of  this 
section,  will  be  able  to  decide  for  themselves  as  to  the  value  of  any 
proposed  material  and  the  possibility  of  successfully  making  alcohol 
from  it  under  their  respective  local  conditions. 

SOURCE  OF  ALCOHOL. 

Alcohol  is  a  substance  produced  by  the  fermentation  of  sugar.  In 
practice  there  are  two  possible  sources  of  sugar  for  this  purpose: 
First,  plants  naturally  containing  sugar  ready  to  be  converted  into 
alcohol  by  simple  fermentation,  such  as  sugar  cane,  sugar  beets,  sor¬ 
ghum,  fruits,  etc.;  second,  materials  containing  starch  which  may  be 
changed  into  sugar  by  the  action  of  malt  or  acids  and  then  fermented, 
such  as  potatoes,  grains,  cassava,  etc.  Alcohol  has  been  and  is  now 
being  made  from  sawdust,  but  as  the  processes  employed  are  trade 
secrets  this  material  will  not  be  discussed. 

NATURE  AND  USE  OF  DENATURED  ALCOHOL. 

The  so-called  “  denatured  alcohol”  is  prepared  by  the  addition  of 
such’  ingredients  as  will  make  the  alcohol  unfit  for  drinking  purposes. 
It  is  used  extensively  in  the  manufacture  of  varnish,  explosives, 
chemicals,  and  many  other  commercial  articles.  It  may  also  be  used, 
in  various  household  appliances,  both  for  lighting  and  heating  pur¬ 
poses  with  much  more  safety  than  either  kerosene  or  gasoline.  Its 
cost  previous  to  the  enactment  of  laws  making  it  tax-free  was  such  as 
to  prevent  its  use  in  engines  and  motors,  consequently  very  little  was 
done  toward  their  adaptation  to  its  use.  It  is,  however,  being  suc- 

5 


410 


6 


POTATO  CULLS  AS  A  SOURCE  OF  INDUSTRIAL  ALCOHOL. 


cossfully  used  in  both  stationary  and  traction  engines  in  other  coun¬ 
tries  where  it  can  be  had  at  a  moderate  price,  and  under  similar  condi¬ 
tions  of  economic  manufacture  would  undoubtedly  be  so  used  in  this 
country. 

CONDITIONS  NECESSARY  FOR  SUCCESSFUL  ALCOHOL  PRO¬ 
DUCTION. 

One  per  cent  of  sugar  or  starch  in  a  product  will  produce  approxi¬ 
mately  one-half  of  1  per  cent  of  alcohol.  It  is  not  practicable  to  distil 
a  fermented  solution  containing  less  than  2  or  3  per  cent  of  alcohol. 
It  is  therefore  evident  that  materials  containing  less  than  6  per  cent 
of  sugar  or  starch  can  not  be  considered  suitable  for  the  profitable  man¬ 
ufacture  of  alcohol.  Many  of  the  waste  materials  of  the  farm  may 
accordingly  be  eliminated  without  further  consideration.  The  next 
point  to  be  considered,  after  it  is  decided  that  the  raw  material  to  be 
used  contains  sufficient  sugar  or  starch,  is  the  supply  of  this  material 
and  the  cost  of  its  delivery  to  the  distillery.  Further,  there  must  be 
available  a  good  supply  of  water  for  the  condensing  apparatus  and 
cheap  fuel  for  the  boilers.  All  of  these  considerations  must  be  care¬ 
fully  weighed  before  any  attempt  is  made  to  establish  a  distillery. 
The  detailed  discussion  which  is  to  follow,  regarding  the  location, 
equipment,  and  operation  of  a  potato  distillery,  is  applicable,  in  a  gen¬ 
eral  way,  to  the  handling  of  other  waste  materials  of  the  farm,  and  will 
be  valuable  as  indicating  the  conditions  under  which  such  materials 
may  be  successfully  used. 

SPECIAL  AVAILABILITY  OF  POTATOES. 

The  reasons  for  limiting  the  detailed  discussion  of  this  bulletin  to 
the  handling  of  potatoes  are  as  follows:  First,  potatoes  have  been 
successfully  used  as  a’ source  of  cheap  alcohol  in  other  countries;  sec¬ 
ond,  conditions  in  this  country  indicate  that  large  quantities  of  potato 
culls  with  the  necessary  starch  content  are  available  for  this  purpose 
at  a  price  which  would  permit  of  the  profitable  manufacture  of  alcohol 
therefrom;  third,  the  experimental  work  of  the  Department  distillery 
has  shown  how  potatoes  can  be  economically  handled  and  practical 
instructions  in  the  methods  of  manufacture  can  now  be  given;  fourth, 
this  work  has  been  done  in  a  small  distillery  such  as  would  be  suitable 
for  large  farms  or  communities  of  farmers  working  in  cooperation. 
These  data  will,  in  our  opinion,  enable  the  farmer  to  convert  frosted 
or  inferior  grades  of  potatoes  into  a  source  of  revenue,  as  it  has  been 
shown  by  the  experiments  that  these  may  bo  made  into  alcohol  at  a 
fair  profit.  The  apparatus  necessary  is  illustrated  and  the  methods 
of  procedure  are  given  in  full.  All  technical  terms  have  been  omitted 
and  the  subject  discussed  from  a  practical  rather  than  a  theoretical 
point  of  view. 

410 


POTATO  CULLS  AS  A  SOURCE  OF  INDUSTRIAL  ALCOHOL.  7 

FUNDAMENTAL  CONSIDERATIONS  IN  ESTABLISHING  A  POTATO 

DISTILLERY. 

LOCATION. 

The  first  consideration  is  that  the  distillery  be  centrally  located 
in  a  potato-raising  country;  second,  that  there  are  railroad  facilities 
for  the  delivery  of  raw  materials  and  fuel  and  the  marketing  of  the 
finished  product  at  a  minimum  expense.  An  abundant  supply  of  cold 
soft  water  is  of  almost  equal  importance.  It  is  desirable  that  the 
plant  be  near  a  creek  or  stream  from  which  the  water  may  be 
obtained  and  into  which  it  may  be  drained  after  serving  its  purpose 
in  the  distillery.  The  character  of  the  water  should  also  be  con¬ 
sidered,  and,  if  possible,  it  should  be  such  that  it  will  not  deposit  a 
scale  on  the  boiler  and  condenser  tubes;  this  difficulty  can  be  over¬ 
come,  however,  by  treating  the  water  with  one  of  the  various  com¬ 
pounds  on  the  market  for  relieving  such  conditions.  The  possibility 
of  handling  and  housing  cattle  to  be  fattened  on  distillery  waste 
should  also  be  considered. 

MACHINERY  AND  EQUIPMENT. 

The  machinery  should  be  such  as  will  permit  of  economy  in  opera¬ 
tion  together  with  a  high  degree  of  efficiency.  As  a  distillery  in 
most  cases  would  not  be  operated  during  the  entire  year,  which 
invariably  means  a  change  in  the  working  force  for  each  season’s 
operation,  and  as  skilled  labor  is  not  always  available,  the  machinery 
should  be  as  simple  as  is  practicable.  It  must  be  remembered, 
however,  that  with  more  costly  machinery  and  apparatus  better 
results  can  be  obtained.  The  equipment  should  be  so  installed  that 
its  operating  cost  will  be  reduced  to  a  minimum,  and  so  arranged  as 
to  allow  any  part  to  be  thrown  out  of  motion  when  not  in  actual  use. 
It  should  be  as  compact  as  possible  without  being  crowded,  and 
permit  the  proper  handling  of  the  material  with  the  least  amount  of 
labor.  The  construction  should  be  such  that  the  exact  result  of 
each  day’s  operation  may  be  easily  ascertained. 

Advantage  should  be  taken  of  the  laws  of  gravity  to  save  pumping 
whenever  possible.  This  can  be  done  by  arranging  the  apparatus  so 
that  each  operation  will  be  made  on  a  higher  level  than  the  succeed¬ 
ing  one;  thus  by  elevating  the  raw  material  to  a  height  suitable 
for  the  first  operation,  it  will  flow  from  one  apparatus  to  another  by 
its  own  weight.  All  machinery  requiring  steam. should  be  placed 
close  to  the  boiler  so  as  to  avoid  condensation  caused  by  long 
pipe  connections.  Exhaust  steam  from  the  engine  and  pumps 
should  be  used  in  the  distilling  apparatus,  and  the  hot  water  from 
the  condensers  should  be  utilized  as  feed  water  for  the  boiler. 


410 


8  POTATO  CULLS  AS  A  SOURCE  OF  INDUSTRIAL  ALCOHOL. 

With  the  exception  of  the  boiler,  each  piece  of  apparatus  should  have 
a  capacity  equal  to  the  exact  amount  of  work  it  is  expected  to  per¬ 
form,  and  should  be  properly  proportioned  to  the  rest  of  the  equip¬ 
ment.  As  the  proper  working  of  each  piece  depends  upon  the 
efficiency  of  the  boiler,  it  is  best  to  have  this  extremely  important 
part  of  the  equipment  of  a  slightly  larger  capacity  than  is  actually 
required,  so  that  it  can  supply  any  piece  of  apparatus  with  more 
than  its  usual  amount  of  steam  in  case  this  should  be  found  neces¬ 
sary.  The  machinery  selected,  therefore,  should  be  simple,  prac¬ 
tical,  efficient,  and  economical. 

The  information  as  to  sizes  and  proportion  of  equipment  can  be 
obtained  from  manufacturers  of  distilling  apparatus  by  informing 
them  as  to  the  kind  and  amount  of  material  to  be  used  and  the  con¬ 
ditions  under  which  the  work  is  to  be  done. 

CONTROL  OF  OPERATION. 

The  economy  of  operation  will  depend  entirely  upon  the  control 
exercised  over  each  piece  of  apparatus  and  each  person  in  the  plant. 
The  capacity  of  each  piece  should  be  known  and  the  results  of  its 
work  observed  each  day,  so  as  to  determine  whether  it  has  been 
overtaxed  or  has  failed  to  do  its  full  share  of  work.  The  entire 
operation  should  be  kept  under  such  control  that  in  case  of  error 
it  may  be  traced  and  attributed  either  to  the  negligence  of  some 
person  or  to  the  inefficiency  of  some  piece  of  apparatus.  A  schedule 
of  each  day’s  operation  should  be  kept,  so  as  to  know  whether  or 
not  the  largest  possible  yields  are  being  obtained  from  the  amount  of 
material  handled. 

It  is  advisable  to  operate  a  distillery  only  during  the  colder  months; 
for  instance,  from  early  autumn  until  late  in  the  spring.  During 
this  time  the  temperature  of  the  cooling  water  will  be  considerably 
lower  than  in  the  warmer  months,  the  amount  required  correspond¬ 
ingly  less,  and  the  time  required  for  cooling  decidedly  shortened. 
This  means  a  shorter  working  day,  and  consequently  less  wear  on  the 
machinery  and  a  considerable  saving  of  fuel.  It  is  essential  that  a 
distillery  be  operated  daily,  and  not  intermittently,  as  each  day’s 
work  depends  in  a  greater  or  less  degree  both  upon  that  of  the  pre¬ 
ceding  and  the  following  day. 

There  is  still  another  very  important  point,  namely,  cleanliness,  and 
upon  this  the  yield  of  alcohol  will  in  a  great  measure  depend.  Mate¬ 
rial  which  is  nutritious  for  yeast  (the  alcohol  ferment)  also  nourishes 
other  organisms,  which  thrive  upon  it  equally  as  well,  but  do  not  pro¬ 
duce  alcohol.  The  presence  of  these  organisms  is  due  to  the  souring 
of  small  bits  of  mash  which  have  not  been  washed  out  of  the  appara¬ 
tus.  This  state  of  affairs  can  easily  be  avoided  by  steaming  or  by 

410 


POTATO  CULLS  AS  A  SOURCE  OF  INDUSTRIAL  ALCOHOL.  Q 

allowing  water  to  flow  through  the  apparatus  at  the  close  of  each  day’s 
work.  Cleanliness  is  especially  necessary  in  the  case  of  the  yeast  and 
fermenting  tubs,  where  the  intrusion  of  these  organisms  will  cause 
serious  trouble.  The  walls  of  the  distillery  should  be  kept  free  from 
mold  by  an  occasional  coat  of  whitewash.  The  floors  should  be 
flooded  daily,  and  the  sewer  connections  must  be  adequate  to  remove 
the  water  and  other  wastes  from  the  premises. 

ESTIMATED  COSTS  OF  A  POTATO  DISTILLERY. 

COST  OF  PLANT. 

The  following  data  give  some  idea  of  the  cost  of  installing  and  oper¬ 
ating  a  plant  of  moderate  capacity  and  the  approximate  value  of  its 
products.  It  will  be  supposed  that  the  plant  under  consideration 
has  a  capacity  for  handling  8,000  pounds  of  potatoes  (equal  to  1,000 
gallons  of  mash)  in  one  working-day  of  ten  hours,  and  that  the  building 
is  one  story  high,  requiring  a  ground  space  of  about  1,000  square  feet. 
The  walls  may  be  constructed  of  any  available  material.  Wood 
sheathing  covered  with  corrugated  galvanized  iron  will  be  economical 
and  serviceable.  In  many  cases  farm  buildings  such  as  barns,  etc., 
could  be  used.  Such  a  building  will  not  cost  more  than  $1,500.  The 
total  cost  of  machinery  and  equipment,  not  including  the  motive 
power,  will  be  about  $9,000.  One  75-horsepower  boiler  and  a  25- 
horsepower  engine  will  be  required,  at  an  additional  cost  of  about 
$1,500.  The  cost  of  erection  need  not  be  considered,  as  a  plant  of 
this  size  would  be  furnished  by  the  manufacturers  in  such  shape 
that  the  purchaser  could  erect  it  himself.  This  would  make  the  total 
investment  amount  approximately  to  $12,000. 

Of  necessity  all  such  estimates  of  the  cost  of  equipment,  operation, 
and  the  value  of  the  output  involve  some  hypothetical  factors  and 
will  vary  under  different  economic  conditions.  The  data  given, 
however,  are  based  on  actual  experience  and  may  be  considered  as 
a  rational  working  basis  on  which  any  individual  may  form  an 
opinion  as  to  the  probability  of  manufacturing  alcohol  successfully, 
from  a  financial  point  of  view,  under  his  own  economic  conditions. 
If  any  one  of  the  factors,  such  as  cost  of  labor  or  of  raw  materials, 
varies  under  locaFconditions  from  the  values  here  used,  due  allowance 
must  be  made  in  working  out  the  individual  problem,  but  the  factors 
to  be  considered  and  the  principles  involved  remain  the  same. 

COST  OF  OPERATION. 

The  expense  of  a  day’s  operation  will  include  the  cost  of  potatoes, 
barley,  fuel,  and  labor.  From  inquiries  made  by  the  Department, 
cull  potatoes  can  be  delivered  at  a  distillery  in  some  potato-growing 
districts  at  25  cents  per  hundred  pounds.  At  this  rate  the  raw 
52473°— Bull.  410—10 - 2 


10  POTATO  CULLS  AS  A  SOURCE  OF  INDUSTRIAL  ALCOHOL. 

material  for  a  day’s  run  of  8,000  pounds  would  cost  $20.  There  will 
be  needed  to  convert  the  starch  in  the  potatoes  into  sugar  the  amount 
of  green  malt  yielded  by  120  pounds  of  barley,  which  at  70  cents  per 
bushel  will  cost  $1.75.  The  cost  of  fuel  will  vary  with  the  skill  of  the 
fireman,  but  with  a  proper  utilization  of  the  fuel  (soft  coal)  1  ton  at 
$4  should  be  sufficient  for  each  day’s  operation.  The  services  of  three 
men  will  bq  required,  namely,  one  competent  foreman  and  two  labor¬ 
ers.  This  will  make  a  total  of  about  $33  for  daily  operating  expense. 

VALUE  OF  OUTPUT. 

The  products  will  consist  of  alcohol  and  “slop.”  As  shown  else¬ 
where  in  this  bulletin,  about  1.3  gallons  of  denatured  alcohol,  180° 
proof,®  can  be  obtained  from  100  pounds  of  potatoes.  The  total 
amount  of  alcohol  produced  per  day  will  therefore  be  about  104  gal¬ 
lons  of  90  per  cent  alcohol,  or  about  187  gallons  of  100°  proof,  or  50 
per  cent  alcohol,  on  which  the  internal -revenue  regulations  are 
based,  which  at  about  40  cents  per  gallon  will  be  worth  $41.60.  There 
will  be  about  1,000  gallons  of  slop.  As  shown  in  the  chapter  on  slop 
feeding,  20  gallons  per  day  per  head  is  sufficient  for  fattening  oxen, 
so  that  the  slop  from  one  day’s  operation  will  form  the  major  portion 
of  rations  for  50  head  of  cattle. 

Such  a  distillery  as  this  is  somewhat  larger  than  is  contemplated 
for  the  so-called  industrial  plant,  being  better  suited  for  a  community 
or  a  cooperative  plant.  A  plant  with  a  capacity  of  100  proof  gallons 
(50  per  cent  alcohol)  per  day  or  less,  designated  by  the  Government  as 
an  industrial  distillery,  for  which  special  regulations  and  privileges 
are  granted,  will  be  better  suited  for  individual  farmers.  The  cost  of 
the  smaller  plant  will  be  less,  but  the  operating  expense  will  not  be 
decreased  in  proportion  to  the  size,  which  makes  the  larger  plant 
more  economical  and  therefore  more  likely  to  succeed.  The  cost 
given  may  be  used  as  a  basis  for  estimating  that  of  a  plant  of  any  size, 
but  the  exact  figures  can  be  obtained  from  the  manufacturers  of 
distillery  machinery. 

GOVERNMENT  REGULATIONS. 

When  the  erection  of  a  distillery  is  contemplated  it  is  necessary 
that  notice  to  that  effect  be  given  to  the  internal-revenue  authorities 
and  that  the  laws  and  regulations  relating  to  such  a  business  be  com¬ 
plied  with.  The  regulations  may  at  first  seem  complicated,  but  they 
are  found  necessary  by  the  Government  in  order  to  prevent  fraud, 
and  can  easily  be  followed  when  one  is  familiar  with  them.  They 
consist  chiefly  of  monthly  reports  to  be  furnished  to  the  Bureau  of 

aIn  the  United  States  “proof  spirit,”  or  100°  proof  alcohol,  is  an  alcoholic  liquor 
containing  one-half  its  volume  of  absolute  alcohol  at  60°  F.  A  product  of  180°  proof 
is  said,  therefore,  to  be  “above  proof,”  and  contains  90  per  cent  of  alcohol  by  volume. 

410 


POTATO  CULLS  AS  A  SOURCE  OF  INDUSTRIAL  ALCOHOL. 


11 


Internal  Revenue  showing  the  amount  of  raw  material  used,  the 
amount  of  alcohol  manufactured,  and  the  disposition  made  of  same. 
Agricultural  distilleries  manufacturing  less  than  100  proof  gallons 
per  day  are  exempt  from  many  of  the  regulations  applying  to  plants  of 
larger  capacity.  All  the  necessary  information  can  be  obtained  by 
applying  to  the  collector  of  internal  revenue  of  the  district  in  which 
the  distillery  is  to  be  located.  Regulation  No.  30,  Revised,  relating 
to  denatured  alcohol,  can  be  had  by  applying  to  the  Bureau  of 
Internal  Revenue,  Washington,  D.  C. 

DETAILS  OF  OPERATING  A  POTATO  DISTILLERY. 

In  manufacturing  alcohol  from  potatoes  they  are  first  washed  and 
then  cooked  so  that  the  starch  present  can  be  readily  converted  into 
sugar  by  the  action  of  malt.  The  sugar  so  formed  is  fermented  by 
the  addition  of  yeast  and  the  alcohol  contained  in  the  fermented 
liquid  is  separated  from  it  by  the  process  of  distillation.  The  detailed 
operation  is  as  follows: 

PREPARATION  OF  THE  MASH. 

The  potatoes,  after  being  weighed  in  the  weighing  bin,  are  run  down  a  slatted  chute 
into  the  cooker  manhole  as  shown  in  figure  1.  The  slats  on  the  underside  of  the  chute 
are  spaced  so  as  to  allow  only  the  sticks  and  dirt  to  fall  through.  When  the  cooker  is 
filled,  the  potatoes  are  washed  by  playing  a  stream  of  water  upon  them  through  the 
manhole,  the  dirt  and  water  being  drained  off  by  means  of  the  escape  valve.  After 
the  potatoes  are  thoroughly  cleaned  the  manhole  cover  is  put  on  and  bolted,  and 
steam  is  admitted  into  the  top  of  the  cooker  by  the  valve  C,  the  escape  valve  being 
left  open  so  as  to  allow  the  condensed  water  to  discharge  at  B.  After  the  potatoes 
have  been  well  warmed  and  steam  begins  to  come  out  of  the  escape  valve,  the  latter 
is  closed.  The  steam  is  then  shut  off  at  the  top  of  the  cooker  and  admitted  at  the 
bottom  through  a  series  of  inlets  from  the  steam  pipe  D.  The  blow-off  valve  E,  at  the 
top  of  the  cooker,  is  now  partially  opened.  By  allowing  a  small  amount  of  steam  to 
escape  from  this  valve  the  potatoes  are  shaken  up  and  thoroughly  disintegrated. 
The  steam  pressure  in  the  cooker  is  now  allowed  to  rise  gradually  to  about  50  or  60 
pounds,  when  the  blow-off  valve  should  be  closed.  The  entire  time  required  for 
warming  the  potatoes  and  reaching  the  maximum  pressure  should  be  about  one  hour. 
The  stirrer  G  is  then  started,  and  the  maximum  pressure  held  for  about  ten  minutes 
to  insure  a  thorough  cooking  of  the  starch  in  the  potatoes,  after  which  the  steam  is 
shut  off. 

The  blow-off  valve  is  then  opened  wide  and  the  temperature  inside  the  cooker 
allowed  to  fall  to  212°  F.  The  temperature  of  the  cooked  potatoes  is  further  reduced 
by  means  of  the  vacuum  pump  to  from  140°  to  145°  F.,  at  which  point  the  malt  (see 
p.  19)  necessary  to  change  the  starch  into  sugar  is  added.  About  2  pounds  of  malt  are 
used  for  each  100  pounds  of  potatoes  mashed,  the  exact  amount  depending  upon  the 
quantity  of  starch  in  the  potatoes  and  the  quality  of  the  malt.  This  proportion  will 
apply  either  in  the  use  of  green  or  dried  malt,  as  the  diastatic  power  (i.  e.,  the  ability 
to  change  starch  into  sugar)  of  each  is  about  the  same. 

Green  malt  is  crushed  between  rolls,  while  dried  malt  is  ground  in  a  mill  before 
using.  About  fifteen  minutes  before  the  mash  in  the  cooker  is  ready  for  malting,  the 
malt,  already  crushed  or  ground,  as  the  case  may  be,  is  mixed  with  water  in  the  propor¬ 
tion  of  1  gallon  of  water  to  2.5  pounds  of  dried  malt,  or  three-fourths  gallon  of  water 
410 


12  POTATO  CULLS  AS  A  SOURCE  OF  INDUSTRIAL  ALCOHOL. 


o 

l-H 


410 


—Mashing  and  fermenting  apparatus  for  potato  distillery. 


POTATO  CULLS  AS  A  SOURCE  OF  INDUSTRIAL  ALCOHOL. 


13 


to  the  same  amount  of  green  malt.  It  is  prepared  in  a  tub  situated  above  the  cooker 
and  allowed  to  drop  into  the  latter  when  the  temperature  of  the  cooked  mash  has  been 
reduced  to  about  140°  or  145°  F.  The  diastase  in  the  malt  will  dissolve  the  cooked 
starch  and  convert  it  into  a  fermentable  sugar.  This  conversion  will  be  complete  in 
about  fifteen  or  twenty  minutes,  during  which  time  the  mash  should  be  constantly 
stirred.  In  order  to  know  whether  or  not  the  conversion  is  complete,  a  few  drops  of 
iodin  solution  «  are  added  to  a  little  mash  which  has  been  filtered  through  a  cheese¬ 
cloth  bag  and  placed  upon  a  porcelain  dish  or  some  other  white  surface.  If  the  mix¬ 
ture  turns  blue  it  indicates  the  presence  of  unconverted 
starch  and  it  is  then  necessary  either  to  increase  the 
amount  of  malt  or  the  time  of  conversion.  Further  tests 
should  be  made  until  the  blue  color  is  no  longer  obtained, 
which  indicates  that  the  change  of  starch  into  sugar  has 
been  completed. 

The  mash  is  now  ready  to  be  cooled  and  sent  to  the 
fermenter,  but  to  insure  easy  handling  through  the  pumps 
and  distilling  apparatus  it  is  necessary  to  remove  the 
skins  and  the  fibrous  or  woody  parts  of  the  potato  which 
have  not  been  broken  up  during  the  cooking  process. 

The  entire  mash  on  leaving  the  cooker,  therefore,  is  run 
through  the  potato-peel  extractor,  which  is  placed  in  the 
drop  tub.  This  consists  of  an  upright  perforated  copper 
cylinder  on  the  inside  of  which  is  a  revolving  spiral, 
which  carries  the  hulls  and  lumps  to  the  top  of  the  cylin¬ 
der,  where  they  are  discharged  through  a  spout,  the  liquid 
portion  flowing  through  the  perforations  into  the  drop 
tub .  The  cleaned  mash  is  now  pumped  through  the  mash 
cooler,  where  it  is  reduced  to  the  so-called  pitching  b  tem¬ 
perature,  by  circulating  a  constant  stream  of  cold  water 
through  a  pipe  surrounding  the  pipe  through  which  the 
mash  passes.  The  pitching  temperature  most  favorable 
for  fermentation  varies  between  60°  and  70°  F.,  depending 
upon  the  weather  conditions  and  the  volume  of  the  mash. 

It  should  be  such  that  the  mash  will  show  signs  of  active 
fermentation  in  a  few  hours  after  being  run  into  the  fer¬ 
menter.  At  the  same  time  that  the  mash  is  run  into  the 
fermenter  the  yeast  mash  (about  3  per  cent  by  volume 
of  the  main  mash)  is  also  added.  It  is  prepared  (see 
chapter  on  yeast,  p.  24)  in  a  tub  placed  above  the  level  of 
the  fermenter,  so  that  it  may  be  easily  discharged  into  it. 

FERMENTING  THE  MASH. 

After  the  yeast  and  mash  are  in  the  fermenter  the  proc¬ 
ess  of  fermentation  will  begin  and  the  sugar  in  solution  FlG-  2.— Apparatus  for  deter- 
be  broken  down  into  alcohol  and  carbon  dioxid  gas.  The  mining  the  specific  gravity  of 

•  i  0  s,  mush 

gas  will  pass  off  into  the  air  and  the  alcohol  remain  in 

the  solution.  At  this  point  it  is  important  to  know  the  gravity  and  acidity  of  the  set 
mash,  as  it  is  now  called.  The  specific  gravity  indicates  the  amount  of  sugar  or  fer¬ 
mentable  material  contained  in  the  mash  and  is  ascertained  as  follows:  The  mash  is 
thoroughly  stirred  and  a  small  portion  filtered  through  a  cheese-cloth  bag  into  a 
suitable  cylinder,  as  shown  in  figure  2.  A  Balling  saccharimeter  is  placed  in  the 

aThe  solution  of  iodin  is  prepared  by  adding  2.5  drams  of  potassium  iodid  and  75 
grains  of  iodin  (which  can  be  bought  at  any  drug  store)  to  1  quart  of  water  and 
shaking  until  thoroughly  dissolved. 

Pitching  the  mash”  means  setting  it  with  the  yeast  to  ferment. 

410 


14 


POTATO  CULLS  AS  A  SOURCE  OF  INDUSTRIAL  ALCOHOL. 


filtered  liquid  and  the  reading  indicated  on  it  at  the  liquor  level  will  be  the  gravity 
of  the  mash.  This  reading  should  be  from  16°  to  18°,  which  means  that  the  mash 
contains  from  16  to  18  percent  of  solids,  most  of  which  is  sugar. 

The  acidity  of  the  set  mash,  or  the  amount  of  acid  present,  is  due  to  the  acidity 
acquired  by  the  yeast  mash  and  the  natural  acidity  of  the  potatoes.  It  is  determined 
by  neutralizing  a  small  portion  of  the  mash  with  a  normal  solution  of  sodium  hydroxid  a 
and  the  amount  of  the  latter  required  will  represent  the  acidity  of  the  mash.  This  is 
done  by  means  of  the  apparatus  shown  in  figure  3.  The  bottle  A  contains  the  solution 
of  sodium  hydroxid .  The  burette  B  used  for  measuring  the  solution  is  filled  by  squeez¬ 
ing  the  rubber  bulb.  A  small  portion  of  the  mash  is  filtered  through  a  filter  paper  and 

20  ce  of  the  filtered  liquid, 
measured  in  the  pipette  C,  are 
poured  into  the  beaker  D. 
The  solution  is  allowed  to  drop 
slowly  from  the  burette  into  the 
beaker,  the  mixture  being  con¬ 
stantly  stirred  until  the  acid 
contained  in  the  filtered  liquid 
has  been  neutralized.  The 
neutral  point  is  determined  by 
placing  a  drop  of  the  mixture 
upon  litmus  paper.  When  it 
will  not  turn  blue  litmus  paper 
red,  nor  red  litmus  paper  blue, 
but  leaves  it  unaltered,  the 
mixture  will  be  neutral,  and 
the  number  of  cubic  centime¬ 
ters  of  the  solution  of  sodium 
hydroxid  used,  which  can  be 
read  directly  from  the  burette, 
will  represent  the  acidity  of 
the  mash  A 

After  the  mash  has  been  set 
about  ten  or  twelve  hours  the 
fermentation  will  become  vig¬ 
orous  and  the  temperature  be¬ 
gin  to  rise  rapidly,  but  it  should 
not  be  allowed  to  go  much 
above  80°  F.,  as  quite  an 
amount  of  alcohol  due  to 
evaporation  would  be  lost  at  a 
higher  temperature.  To  pre¬ 
vent  further  rise  in  tempera¬ 
ture,  it  is  necessary  to  equip 
the  fermenter  with  a  coil 
through  which  cold  water  is 
circulated.  This  coil  is  so 
arranged  that  it  may  be  raised  or  lowered  very  slowly  in  the  mash  by  means  of  a 
suitable  device,  the  simplest  way  being  by  the  conversion  of  the  circular  motion  of  a 
pulley  into  an  up-and-down  motion  by  means  of  a  rope  and  tackle.  The  fermentation 
is  allowed  to  continue  at  a  temperature  between  60°  to  80°  F.  for  seventy-two  hours, 
except  in  the  case  of  mashes  made  the  latter  part  of  the  week,  when  it  goes  on  for 
ninety-six  hours,  as  no  distillations  may  be  made  on  Sunday.  At  the  end  of  this  time 
the  fermentation  will  be  complete,  provided  the  yeast  was  in  a  normal  condition. 

a  This  solution  can  be  bought  already  prepared  of  any  chemical  supply  house. 

&  All  acidities  given  in  this  bulletin  were  determined  on  this  basis. 

410 


POTATO  CULLS  AS  A  SOURCE  OF  INDUSTRIAL  ALCOHOL. 


15 


DETERMINATION  OF  THE  GRAVITY  AND  ACIDITY  OF  THE 

FERMENTED  MASH. 

To  find  out  how  much  of  the  fermentable  material  originally  contained  in  the  mash 
has  been  utilized  (i.  e./the  amount  of  sugar  that  has  been  converted  into  alcohol),  it 
is  necessary  to  determine  the  gravity  of  the  fermented  mash  (as  shown  in  figure  2), 
which  should  have  gone  down  to  about  1.5  to  2  on  the  saccharimeter.  It  is  also  ex¬ 
tremely  important  that  the  acidity  of  the  fermented  mash  be  determined  and  com¬ 
pared  with  that  of  the  unfermented  or  set  mash.  The  acidity  should  remain  about  the 
same  during  the  entire  fermentation,  but  in  some  cases  there  may  be  a  slight  increase. 
The  fermentation  can  withstand,  and,  in  fact,  is  protected  by,  a  certain  amount  of 
acid,  but  the  presence  of  an  excess  will  seriously  interfere  with  its  progress.  A  large 
increase  in  acidity  in  the  fermenters  is  generally  due  to  the  formation  of  butyric  acid, 
which  is  highly  objectionable.  This  acid  can  be  readily  detected  by  its  odor,  which 
resembles  that  of  rank  butter  and  is  caused  by  allowing  portions  of  fermented  mash  to 
sour  in  the  fermenters,  or  by  not  thoroughly  cleaning  them  after  each  use.  Such  a  con¬ 
dition  can  be  prevented  or  removed  by  scrubbing  the  fermenters,  as  soon  as  they  are 
emptied,  with  a  5  per  cent  solution  of  formalin  or  other  powerful  disinfectant,  or  by 
applying  a  coat  of  whitewash  to  the  inside  of  the  fermenters  and  washing  it  off  before 
refilling.  In  order  to  control  the  fermentation  properly,  the  gravity  and  acidity  of 
the  mash  are  determined  every  twenty-four  hours  and  a  record  kept,  as  shown  in  the 
following  form: 

Mashing ,  fermentation ,  and  distillation  record. 

Experimental  Distillery  No.  1.  Located  at  Washington. 


Fermenter  No.  3.  Set  January  22.  Distilled  January  25. 

MASHING  RECORD. 

Materials. 

4 


Kinds. 

Y east  mash. 

Main  mash. 

Total. 

Starch. 

Potatoes . 

Pounds. 

400 

25 

Gallons. 

50 

Pounds. 

7,600 

156 

Gallons. 

950 

Pounds. 

8,000 

Gallons. 

1,000 

Per  cent. 
17 

Green  malt . 

FERMENTATION  RECORD. 


Yeast  mash. 

Main  mash. 

Date'. 

°Balling. 

Temper¬ 

ature. 

Acidity. 

Date. 

°Balling. 

Temper¬ 

ature. 

Acidity. 

1910. 

op. 

1910. 

°F. 

January  20 . 

22 

132 

0.8 

January  22 . 

18.0 

67 

0.70 

“21... 

22 

65 

2.5 

'  23 . 

10.6 

77 

.75 

22... 

5 

77 

2.5 

24 . 

3.5 

77 

.75 

25 . 

1.5 

75 

.75 

DISTILLATION  RECORD. 

Wine  gallons .  104  Proof . 180°  Proof  gallons . 187 


As  before  stated,  the  gravity  should  fall  rapidly  and  the  acidity  remain  about  the 
same  or  increase  slightly.  If  this  is  not  the  case,  the  mash  has  either  been  pitched 
at  a  temperature  too  low  for  the  proper  development  of  the  yeast,  or  acid-forming 
organisms  have  become  active  and  are  retarding  the  fermentation.  If  tempera- 
410 


16  POTATO  CULLS  AS  A  SOURCE  OF  INDUSTRIAL  ALCOHOL. 


ture  conditions  have  been  the  cause,  the  following  mash  can  be  pitched  a  little  higher; 
but  if  injurious  organisms  have  gained  control  in  the  mash,  they  must  be  suppressed 
at  once  so  as  to  prevent  the  following  mashes  from  becoming  infected  also.  The 
amount  of  alcohol  contained  in  the  fermented  mash  will  vary  according  to  the  gravity 
of  the  set  mash,  and  as  alcohol  boils  at  a  lower  temperature  than  the  other  constituents 
it  can  be  separated  by  distillation. 

DISTILLING  THE  ALCOHOL. 

In  figure  4  is  shown  a  distilling  apparatus  especially  adapted  for  the  economic 
separation  of  the  alcohol  from  the  mash.  It  is  not  complicated,  as  it  might  appear 
at  first  glance,  but  is  decidedly  simple  and  requires  little  attention  after  it  has  been 
once  regulated.  The  fermented  mash  is  pumped  slowly  into  the  distilling  appa¬ 
ratus,  where  it  is  brought  in  contact  with  live  steam,  which  boils  it  and  carries  off 
the  alcohol  in  the  form  of  vapor,  which  in  turn  is  passed  through  a  condenser, 
where  it  is  reduced  to  a  liquid.  The  distilling  apparatus  consists  of  two  copper 
columns,  A  and  B,  A  being  used  to  distil  the  alcohol  from  the  mash  and  deliver  it 
in  the  form  of  vapor  to  B ,  where  it  is  redistilled  and  raised  to  the  desired  strength. 

The  apparatus  is  operated  as  follows: 

The  fermented  mash  is  continually  discharged  from  pump  1  and  pipe  2  into  the 
mash  heater  3.  This  heater  contains  a  series  of  tubes  through  which  the  mash  is 
passed  and  around  which  the  vapors  coming  from  the  boiling  mash  in  A  on  their  way 
to  B  are  circulated.  The  heated  mash  leaves  the  heater  through  pipe  4  and  reenters 
the  column  below  the  heater  where  it  comes  in  contact  with  steam.  The  lower  part 
of  the  column  is  divided  by  plates  into  a  series  of  chambers  in  each  of  which  the  mash 
is  boiled  and  relieved  of  some  of  its  alcohol.  The  mash  takes  a  downward  course 
through  the  drop  pipes  and  across  each  of  the  various  plates.  It  will  lose  all  of  its  alcohol 
by  the  time  it  reaches  the  bottom  chamber  of  the  column,  from  which  it  is  automat¬ 
ically  discharged  through  valve  5.  The  shaded  lines  show  its  course.  A  small  por¬ 
tion  of  the  vapors  in  the  bottom  chamber  of  column  A  is  delivered  by  pipe  6  to  the 
condenser  7,  where  it  is  condensed  and  tested  to  ascertain  if  there  is  any  alcohol 
being  lost  in  the  ‘‘slop,”  as  the  discharged  mash  is  ordinarily  called. 

The  steam  necessary  to  boil  the  mash  is  admitted  into  the  bottom  chamber  of  col¬ 
umn  A  through  the  pipe  8.  It  boils  the  mash  in  this  chamber  and  passes  upward 
through  each  succeeding  chamber,  boiling  the  descending  mash  and  carrying  with 
it  the  alcoholic  vapors.  The  plates  within  column  A  are  perforated  so  as  to  allow 
the  steam  to  pass  through  them,  but  the  mash  is  prevented  from  falling  through  the 
perforations  by  the  steam  pressure.  The  vapors  rise  to  the  upper  part  of  column  A 
and  are  conveyed  through  the  pipe  9  into  the  heater  3,  where  they  are  circulated 
about  the  tubes  containing  the  mash  passing  through  the  heater,  and  then  are  carried 
through  the  pipe  10  into  the  bottom  of  column  B. 

The  vapors  coming  from  A  contain  a  considerable  amount  of  moisture  and  other 
impurities  of  which  they  are  freed  in  column  B ,  which  contains  a  series  of  chambers 
upon  each  of  which  is  carried  about  3  inches  of  liquid.  A  constant  level  is  main¬ 
tained  in  each  chamber  by  means  of  the  drop  pipes.  The  plates  between  the  cham¬ 
bers  are  not  perforated  as  in  column  A,  but  the  vapors  ascend  from  one  chamber  to 
another  through  a  pipe  in  the  center  of  the  plate  and  are  deflected  downward  hy  a 
hood  over  the  pipe  and  forced  to  boil  their  way  through  the  liquid  on  each  plate. 
The  arrows  indicate  their  course.  The  vapors  boil  from  chamber  to  chamber,  becom¬ 
ing  purer  as  they  ascend  until  they  reach  the  top  chamber  of  the  column,  from 
which  they  are  delivered  through  the  pipe  11  into  the  cooler  12,  where  they  are  par¬ 
tially  cooled.  From  the  cooler  they  pass  through  pipe  13  into  the  condenser  14, 
where  they  are  reduced  to  a  liquid.  This  cooling  and  condensing  is  effected  by 
circulating  cold  water  around  the  tubes  containing  the  vapor. 

410 


POTATO  CULLS  AS  A  SOURCE  OF  INDUSTRIAL  ALCOHOL 


17 


52473°— Bull.  410—10—3 


18  POTATO  CULLS  AS  A  SOURCE  OF  INDUSTRIAL  ALCOHOL. 


The  condensed  vapor,  or  alcohol  as  it  is  now  called,  is  drawn  off  at  the  bottom  of 
the  condenser  and  allowed  to  flow  through  the  test  box  15,  where  it  can  be  examined 
as  to  its  purity  and  strength.  As  the  mash  and  steam  are  admitted  continuously 
into  the  apparatus,  the  flow  of  the  alcohol  from  it  will  also  be  continuous.  The  steam 
pressure  within  the  apparatus  is  registered  by  the  pressure  gauge  16.  The  alcohol 
after  passing  through  the  test  box  is  run  into  the  storage  tank  17  (which  is  sufficiently 
large  to  hold  several  days’  product)  to  be  denatured. 

DENATURING  THE  ALCOHOL. 

The  denaturing  process  consists  in  adding  certain  ingredients  to  the  alcohol  to  make 

it  unfit  for  drinking  purposes.  Alcohol  to 
be  denatured  must  be  at  least  180°  proof, 
which  is  equivalent  to  90  percent  alcohol, 
and  the  ingredients  used  must  be  author¬ 
ized  by  the  Bureau  of  Internal  Revenue 
and  the  denaturing  done  under  its  super¬ 
vision.  Wood  alcohol  and  benzin  are  gen¬ 
erally  used  as  denaturing  agents,  though 
the  Bureau  of  Internal  Revenue  allows  the 
use  of  other  agents,  depending  upon  the 
use  to  which  the  denatured  alcohol  is  to 
be  put.  (See  Regulations  30,  Supplement 
No.  1,  U.  S.  Internal  Revenue,  or  Bulle¬ 
tin  130,  U.  S.  Department  of  Agriculture, 
Bureau  of  Chemistry,  p.  161.) 

YIELD  OF  ALCOHOL. 

The  yield  of  alcohol  obtainable  from  pota¬ 
toes  is  directly  proportionate  to  the  amount 
of  starch  which  they  contain,  so  that  it  is 
important  to  know  not  only  the  weight  of  a 
consignment,  but  also  the  percentage  of 
starch.  This  is  of  course  absolutely  neces¬ 
sary  when  the  potatoes  are  paid  for  on  the 
basis  of  their  starch  content,  which  is  their 
real  alcohol-producing  value.  The  per¬ 
centage  of  starch  may  be  easily  determined 
by  means  of  an  instrument  especially  de¬ 
signed  for  that  purpose,  which  is  illustrated 
in  figure  5.  An  average  sample  of  the  pota¬ 
toes  is  washed  and  thoroughly  dried.  Ex¬ 
actly  10  pounds  are  placed  in  the  wire  bas¬ 
ket  (one  potato  may  be  cut  if  necessary  to 
get  the  exact  weight) .  The  instrument  with 
the  basket  attached  is  floated  in  a  tank  con¬ 
taining  clear  water  at  63.5°  F.  The  stem  is  so  graduated  that  the  percentage  of  the 
starch  can  be  read  directly  from  it.  Potatoes  average  from  14  to  20  per  cent  of  starch 
and  1  pound  of  starch  in  practice  yields  about  0.071  gallon  of  absolute  alcohol,  or  0.079 
gallon  of  denatured  alcohol  at  180°  proof.  One  hundred  pounds  of  an  average  grade 
of  potatoes  containing  17  per  cent  of  starch  would  yield  approximately  1.3  gallons  of 
denatured  alcohol. 


Fig.  5.— Apparatus  for  determining  the  starch 
content  of  potatoes. 


410 


POTATO  CULLS  AS  A  SOURCE  OF  INDUSTRIAL  ALCOHOL. 


19 


MALT. 

DIASTATIC  POWER  OF  MALT. 

Malt  is  sprouted  grain,  which  during  its  period  of  sprouting  has 
developed  diastase,  a  substance  which  under  certain  conditions  pos¬ 
sesses  the  power  of  changing  starch  into  sugar.  It  is  used,  there¬ 
fore,  in  converting  the  starch  of  potatoes,  corn,  and  other  raw  prod¬ 
ucts  into  a  fermentable  material.  It  is  judged  as  to  its  value  by  the 
amount  of  diastase  which  it  contains,  and  its  ability  to  convert  starch 
is  called  its  “diastatic  power.”  Malt  may  be  used  either  while  it  is 
sprouting,  when  it  is  known  as  green  malt,  or  it  may  be  dried  after 
the  sprouting  period  and  used  at  any  time,  in  which  case  it  is  called 
“  dried  malt.”  Dried  malt  can  be  obtained  in  most  sections  of  the 
country  from  the  large  malting  concerns  in  the  shape  of  distiller's 
malt,  and  up  to  the  present  time  has  been  used  almost  exclusively 
in  the  manufacture  of  alcohol.  Experiments  made  by  this  Depart¬ 
ment  during  the  past  year  have  shown  that  for  the  manufacture  of 
denatured  alcohol  the  use  of  green  malt  is  preferable.  It  has  been 
found  that  a  green  malt  with  a  high  diastatic  power  can  be  manufac¬ 
tured  on  the  distillery  premises  for  about  one-half  the  cost  of  dried 
malt.  The  relative  values  of  green  malt  made  from  various  grains 
are  shown  on  page  22. 

PREPARATION  OF  GREEN  BARLEY  MALT. 

The  principle  employed  in  malting  is  practically  the  same  for  ail  grains,  there  being 
two  operations,  namely,  the  soaking  or  steeping  and  the  sprouting  or  growing.  These 
operations  vary  only  in  a  slight  degree  with  different  grains  according  to  their  nature. 
The  steeping  consists  of  soaking  the  grain  in  water  until  it  has  absorbed  sufficient 
moisture  to  enable  it  to  sprout  when  spread  upon  the  malting  floor.  A  good  grade  of 
barley  and  one  that  has  been  harvested  for  at  least  three  months  should  be  selected 
for  malting  purposes. 

Steeping  the  Grain. 

The  style  of  steeping  tank  shown  in  figure  6  is  best  suited  for  this  purpose.  It  should 
be  made  of  iron  and  mounted  on  rollers,  so  that  it  can  be  easily  moved  to  that  part  of 
the  floor  where  the  grain  is  to  be  spread  and  grown.  The  tank  is  partly  filled  with  clear, 
fresh  water  from  A,  and  the  barley  allowed  to  run  in  slowly.  The  chaff  and  weed 
seeds  in  the  grain  will  remain  on  the  surface  of  the  water,  and  can  be  easily  floated 
out  through  the  overflow  B  by  adding  water  until  its  level  rises  to  that  point.  The 
grain  should  be  thoroughly  washed  by  running  water  through  the  tank,  to  be  drained 
off  at  C.  After  the  grain  has  been  thoroughly  cleaned  it  is  covered  with  water  and 
allowed  to  stand  twelve  hours,  the  water  being  replaced  once  or  twice  during  this  time. 
The  water  is  then  drained  off  and  the  grain  allowed  to  stand  for  twelve  hours.  This 
operation  is  repeated  during  the  next  twenty-four  hours.  The  steeping  which  has 
now  continued  for  two  days  will  in  most  cases  be  complete;  however,  it  is  advisable 
sometimes  to  continue  it  for  from  twelve  to  twenty-four  hours  longer.  The  duration 
of  the  steeping  will  depend  principally  upon  the  size  of  the  grain  and  the  temperature 
of  the  water.  Corn,  for  example,  will  require  a  longer  time  to  steep  than  barley,  and 
a  large  kernel  of  any  grain  a  correspondingly  longer  time  than  a  small  kernel  of  the 
410 


20  POTATO  CULLS  AS  A  SOURCE  OF  INDUSTRIAL  ALCOHOL. 


same  kind.  It  is,  therefore,  important  that  grain  of  a  uniform  size  be  selected  in  order 
that  the  steeping  may  be  even. 

It  is  impossible  to  fix  a  definite  length  of  time  for  this  operation.  However,  this  is 
not  important,  as  a  slightly  insufficient  steeping  or  a  little  oversteeping  will  not  make 
any  material  difference;  the  former  is  less  dangerous  than  the  latter,  because  in  the 
case  of  insufficient  steeping  the  grain  may  be  sprinkled  after  it  has  been  placed  upon 
the  floor,  while  in  the  case  of  oversteeping  it  is  liable  to  rot.  When  the  grain  can  be 
crushed  between  the  thumb  and  fingers  and  the  inside  is  not  hard  and  glassy,  but  has 
become  soft  and  chalk-like,  the  steeping  is  completed.  The  grain  is  then  ready  to  be 

dropped  upon  the 
floor  through  the 
valve  D  to  be 
sprouted  or  grown, 
as  it  is  ordinarily 
called. 

Sprouting-  the 
G-rain. 

The  floor  on 
which  the  grain  is 
grown  should  be 
smooth,  preferably 
of  cement,  with  a 
slight  slope  so  as 
to  allow  the  water 
used  in  sprinkling 
to  drain  off,  and 
also  to  perm  i  t  an  oc- 
casional  scrubbing 
to  keep  it  free  from 
mold  and  putre¬ 
factive  organisms. 
When  the  grain 
is  first  dropped 
it  is  spread  in  a 
layer  about  6  or 
8  inches  deep  and 
the  steeping  water 
is  allowed  to  drain 
off  for  five  or  six 
hours.  The  grain 

Fig.  6. — Barley  steeping  tank.  then  heaped  up 

in  a  pile,  or  couch 

as  it  is  called,  from  10  to  12  inches  high.  In  about  twenty-four  hours  the  root¬ 
lets,  at  first  resembling  white  points,  force  their  way  through  the  husks  of  the 
grain;  these  grow  rapidly,  and  evolve  heat  which  raises  the  temperature  of  the  grain 
perceptibly.  It  is  important  that  the  temperature  of  the  malt  while  on  the  floor  be 
kept  as  near  60°  F.  as  possible,  or  slightly  below  this  temperature.  To  do  this  it  is  nec¬ 
essary  to  reduce  the  height  of  the  piles  gradually  to  about  3  inches  and  to  turn  the 
grain  frequently,  at  least  twice  a  day.  A  wooden  shovel  serves  best  for  this  purpose, 
as  it  is  light,  and  permits  the  throwing  of  the  grain  high  into  the  air,  which  greatly 
increases  the  vitality  of  the  growing  malt.  Care  should  be  taken  not  to  crush  the 
410 


POTATO  CULLS  AS  A  SOURCE  OF  INDUSTRIAL  ALCOHOL. 


21 


•  grains  during  the  turning,  as  crushed  grains  encourage  the  growth  of  mold,  for  which 
reason  it  is  advisable  to  wear  felt-soled  shoes  on  the  malting  floor.  After  the  grain  has 
grown  for  from  six  to  eight  days  the  sprout,  or  “acrospire,”  which  has  been  develop¬ 
ing  inside  of  the  husk  forces  its  way  out  at  the  end  of  the  grain  opposite  to  the  rootlet. 
The  malt  may  be  used  with  excellent  results  at  this  time,  but  with  a  longer  period  of 
growth  the  diastatic  power  is  considerably  increased.  The  sprouting,  therefore,  is 
allowed  to  continue  slowly  for  another  six  or  eight  days,  or  even  longer,  until  the 
acrospire  has  attained  a  length  three  or  four  times  that  of  the  grain.  The  length  of 
the  rootlet  and  acrospire,  however,  do  not  necessarily  indicate  the  quality  of  the  malt, 
as  the  slower  the  growth  and  the  longer  the  period  of  growing  the  higher  will  be  the 
diastatic  power,  the  extent  of  the  growth  being  equal.  The  aim  while  the  grain  is 
on  the  floor  is,  therefore,  to  have  it  grow  as  slowly  as  possible  without  allowing  it  to 
wither.  It  may  be  sprinkled  occasionally  if  necessary  to  keep  it  in  a  moist  and  healthy 
condition. 


Figure  7  shows  the  different  stages  of  the  growing  grain:  (1)  The  grain  as  it  leaves 
the  steeping  tank;  (2)  the  rootlet  breaking  through  the  husk;  (3  and  4)  the  develop¬ 
ment  of  the  rootlet  and 
sprout;  (5)  the  sprout 
broken  through  the  husk 
(at  this  point  the  grain  has 
grown  for  a  period  of  about 
six  days);  (6  and  7)  the 
malt  as  it  should  appear 
after  growing  for  fifteen  or 
twenty  days,  at  which  time 
the  diastatic  power  will  be 
very  high.  After  the  last 
period  the  diastatic  power 
will  decrease,  as  the  grain 
withers.  In  order  to  save 
labor  the  amount  of  barley 
required  for  two  or  three 

days’  operation  may  be  steeped  and  malted  at  the  same  time,  as  it  may  remain  upon 
the  floor  a  few  days,  more  or  less,  without  any  appreciable  change.  If  the  malt  has 
been  properly  handled  it  will  have  increased  its  original  weight  by  about  50  percent. 

It  is  absolutely  essential  that  the  grain  be  turned  at  least  twice  a  day  from  the 
time  it  is  put  on  the  floor  until  it  is  used.  The  malting  room  should  be  kept  as  near 
a  constant  temperature  as  possible,  and  so  arranged  as  to  allow  sufficient  ventilation 
and  prevent  strong  drafts  of  air  from  coming  in  contact  with  the  grain.  It  is  preferable 
to  have  the  floor  below  the  level  of  the  surface  of  the  earth,  about  the  depth  of  an 
ordinary  cellar,  so  that  its  temperature  will  not  be  easily  influenced  by  weather  condi¬ 
tions.  Briefly,  then,  a  good  barley  malt  can  only  be  obtained  from  a  good  grade  of 
barley  properly  steeped  and  grown  for  a  long  interval  of  time  (twelve  to  twenty  days) 
with  a  fair  amount  of  moisture,  at  a  temperature  not  to  exceed  60°  to  63°  F. 


Fig.  7.— A  sprouting  grain  of  barley  at  d  ifferent  stages  of  development. 


CRUSHING  THE  GREEN  MALT. 


In  order  to  get  the  benefit  of  the  total  amount  of  diastase  developed  it  is  necessary 
that  the  malt  be  thoroughly  crushed;  this  should  be  done  a  short  time  before  using. 
The  crusher  shown  in  figure  8  is  of  the  type  generally  used.  It  is  advisable  to  pass 
the  malt  through  the  crusher  twice,  in  order  to  insure  that  it  is  completely  crushed 
and  the  diastase  released  from  the  grains,  thus  permitting  of  its  ready  diffusion  through 
the  material  upon  which  it  is  to  act. 

410 


22 


POTATO  CULLS  AS  A  SOURCE  OF  INDUSTRIAL  ALCOHOL. 


PREPARATION  AND  VALUE  OF  GREEN  MALT  FROM  VARIOUS 

GRAINS. 

While  experience  shows  that  barley  is  best  suited  for  malting  purposes,  it  may 
be  necessary  sometimes  when  it  is  not  available  to  use  other  grains.  The  following 
table  gives  the  details  of  preparation  and  the  relative  values  of  green  malt  made  from 
other  sources: 


Preparation  of  green  malt  from  various  grains  and  their  respective  values. 


Kind  of  grain. 

Time  re¬ 
quired  for 
steeping. 

Tempera^ 
ture  of 
steeping 
water. 

Tempera¬ 
ture  main¬ 
tained  on 
floor. 

Time  re¬ 
quired  for 
sprouting. 

Diastatic 

power. 

/ 

Hours. 

O  p 

o  p 

Days. 

Barley . 

48-GO 

60 

60 

12-20 

1,200-1,400 

Wheat . 

36-48 

55 

60 

8-16 

800-1,000 

Rye . 

15-24 

55 

60 

8-16 

300-  350 

Oats . 

24-36 

60 

65 

8-12 

200-  250 

Corn . 

72-96 

70 

75 

8-10 

100-  150 

Fig.  8. — Green  malt  crusher. 


The  diastatic  power,  shown  in  the  last  column,  is  measured  by  allowing  1  cc  of 
malt  extract  (25  grams  of  malt  containing  approximately  50  per  cent  of  moisture  to 
500  cc  of  water  digested  for  four  hours  at  ordinary  temperature)  to  act  upon  100  cc 
410 


POTATO  CULLS  AS  A  SOURCE  OF  INDUSTRIAL  ALCOHOL. 


23 


of  a  2  per  cent  solution  of  soluble  starch  for  one  hour  at  room  temperature.  The 
amount  of  maltose  is  determined  by  weighing  the  copper  oxid  precipitated  from 
Fehling’s  solution.  The  figures  given  under  “  diastatic  power  ”  represent  the  number 
of  grams  of  maltose  which  100  grams  of  malt  will  produce. 

Wheat  is  the  only  grain  that  shows  even  a  fair  value  as  compared  with  barley;  the 
others  are  not  only  markedly  inferior  in  diastatic  power  but  are  also  rather  difficult 
to  prepare,  especially  corn.  For  these  reasons  they  are  not  to  be  considered  as  a  pos¬ 
sible  source  of  malt  at  the  present  time.  Barley  is  very  easy  to  handle  during  the 
malting  process,  and  as  it  can  be  obtained  in  most  sections  of  the  country  it  is  gener¬ 
ally  used. 

RELATIVE  VALUE  OF  GREEN  AND  DRIED  MALT. 

A  series  of  experimental  mashes  were  run  in  which  various  amounts  of  green  malt 
were  allowed  to  act  upon  equal  quantities  of  starch.  The  results  obtained  are  given  in 
the  following  table: 

Results  obtained  on  seven  mashes  using  varying  amounts  of  green  malt. 


Number  of  mash. 


U'AV<X. 

1. 

2. 

3. 

4. 

5. 

6. 

7. 

Mash: 

Amount  of  malt  (pounds) . 

3.2 

3.72 

3.92 

4.3 

5.12 

5.4 

5.67 

Amount  of  potatoes  (pounds) . 

160 

160 

160 

160 

160 

160 

160 

Total  mash  (gallons) . 

20 

20 

20 

20 

20 

20 

20 

Yeast  mash  added  (gallons) . 

1 

1 

1 

1 

1 

1 

1 

Set  mash: 

Saccharimeter  reading . 

17.6 

17.6 

17.4 

17.6 

17.5 

17.7 

17.7 

Acidity  (cc) . 

.7 

.7 

.7 

.7 

.  7 

.7 

.7 

Fermented  mash: 

Saccharimeter  reading . 

1.3 

2.2 

1.4 

1.3 

1.8 

1.5 

1.9 

Acidity  (cc) . 

.  85 

.85 

.85 

.8 

.  95 

.  95 

1.6 

Temperature  during  fermentation  (°F.)... 

60-80 

60-80 

60-80 

60-80 

60-80 

60-80 

60-80 

Reducing  sugar  in  100  cc  (grams) . 

0.12 

0.23 

0.11 

0.14 

0.14 

0. 13 

0.  24 

Starch  (per  cent) . 

.10 

.38 

.27 

.26 

.44 

.49 

.50 

Alcohol  by  volume  (per  cent) . 

8.4 

7.9 

8.4 

8.3 

8.2 

8.3 

8.1 

For  mash  No.  1,  in  which  the  smallest  amount  of  green  malt  was  used,  the  sac¬ 
charimeter  reading  of  the  fermented  mash  is  as  low  as  that  of  any  of  the  other  mashes. 
The  amount  of  reducing  sugars  and  the  percentage  of  starch  present  in  the  fermented 
mashes  increase  with  the  larger  amount  of  malt  used.  This  proves  that  all  the  starch 
contained  in  the  potatoes  was  converted  as  completely  in  the  mash  containing  the 
smallest  amount  of  malt  as  in  those  for  which  considerably  more  was  used,  and  that 
the  starch  and  sugar  present  in  the  fermented  mash  was  contained  in  the  malt  itself, 
and  so  held  within  it  as  to  prevent  its  being  acted  upon  during  the  fermentation.  The 
high  percentage  of  alcohol  contained  in  mash  No.  1  as  compared  with  that  of  the  others 
also  indicates  that  this  mash  contained  a  sufficient  amount  of  malt  to  completely  con¬ 
vert  its  starch.  In  other  words,  3.2  pounds  of  malt  is  enough  to  convert  the  starch  in 
1G0  pounds  of  potatoes,  or  about  2  pounds  for  each  100  pounds  of  potatoes.  The  pota¬ 
toes  used  in  these  mashes  contained  16  per  cent  of  starch,  so  that  each  pound  of  malt 
converted  8  pounds  of  starch. 

In  large  distilleries  where  corn  is  used  in  the  manufacture  of  alcohol  it  is  considered 
an  economical  practice  to  use  8  pounds  of  dried  malt  for  each  100  pounds  of  corn.  As 
corn  contains  approximately  60  per  cent  of  starch  it  is  seen  that  1  pound  of  dried  malt 
also  converts  about  8  pounds  of  starch,  so  that,  pound  for  pound,  the  value  of  green  and 
dried  malt  is  about  the  same.  The  amount  of  green  malt,  however,  which  can  be 
manufactured  from  a  certain  amount  of  barley  is  double  that  of  dried  malt,  so  that  the 
cost  of  using  the  latter  will  be  twice  as  much. 

410 


24  POTATO  CULLS  AS  A  SOURCE  OF  INDUSTRIAL  ALCOHOL. 


YEAST. a 

DEVELOPMENT  OF  YEAST. 

Yeast  is  an  exceedingly  small  plant  that  grows  and  reproduces  itself  in  liquids  con¬ 
taining  sugar.  During  its  development  it  decomposes  the  sugar  and  forms  alcohol  by 
the  process  known  as  fermentation.  It  is  generally  seen  in  the  shape  of  a  compressed 
cake,  consisting  of  a  great  number  of  minute  cells,  each  of  which  is  a  distinct  plant, 
capable  of  further  reproduction,  which  has  been  separated  from  the  liquid  in  which  it 
was  grown.  The  cells  grow  ordinarily  by  budding  or  sprouting,  as  shown  in  figure  9. 
The  older  or  mother  cells  will  bud  and  form  young  or  daughter  cells  which  cling  to  the 
parents  for  a  time  and  then  separate  and  become  parent  cells  in  their  turn.  Both 

parent  and  daughter  cells  continue  to  bud  as  long  as  there  is  any  sugar  in  the  liquid, 

and  each  one  forms  a  new  cell  about  every  twenty  minutes.  Figure  10  shows  the  growth 
and  reproduction  of  yeast  cells  as  seen  under  the  microscope,  the  cells  being  too  small 
to  be  seen  with  the  naked  eye. 

SPONTANEOUS  AND  PURE  CULTURE  YEASTS. 

Yeast  cells  are  blown  about  in  the  air,  as  is  evidenced  by  the  fact  that  they  are  found 
upon  various  fruits  containing  sugar.  It  is  their  presence  that  causes  grape  juice, 

cider,  etc.,  to  ferment.  Also  if  a  liquid  which  contains 
sugar,  but  in  which  there  is  no  yeast,  is  exposed  to  the 
open  air,  fermentation  will  begin  after  several  hours. 
This  is  due  to  the  yeasts  which  have  fallen  into  the 

liquid  from  the  air  and  become  active.  Such  a  fer¬ 

mentation  is  called  “ spontaneous”  or  “wild  yeast” 
fermentation  because  it  takes  place  of  its  own  accord 
and  is  distinguished  from  the  so-called  “pure-culture 
yeast  fermentation  ”  in  that  it  can  not  be  controlled. 

Spontaneous  fermentation  can  not  be  used  in  the 
practical  manufacture  of  alcohol  inasmuch  as  it  can 
not  be  relied  upon  to  take  place  in  short  and  regular 
periods  of  time;  it  is  therefore  customary  to  add  cer¬ 
tain  amounts  of  yeast.  A  hop  yeast  originating  from 
cells  in  the  air  or  a  pure-culture  yeast  may  be  used. 

The  latter  is  obtained  by  isolating  a  single  cell  of  a 
Fig.  9.— Development  of  a  yeast  ,  ,  ,  .  ,  .  ,  .  ...  .. 

eell  yeast  that  has  been  found  to  be  especially  effective 

for  alcoholic  fermentation  and  cultivating  it  carefully 
so  that  it  can  be  used  as  a  start  or  seed  yeast  at  any  time.  The  term  “pure  culture  ” 
applies  to  the  method  of  handling  a  yeast  and  not  to  any  particular  kind.  If  a  single 
cell  of  any  wild  yeast  is  separated  from  all  other  organisms  and  allowed  to  grow  in 
complete  isolation,  a  yeast  will  be  obtained  which  will  have  all  the  characteristics 
of  the  original  single  cell  and  is  then  known  as  a  pure-culture  yeast. 

There  are  a  great  many  varieties  of  yeasts,  differing  in  value  for  the  various  com¬ 
mercial  uses.  Some  are  best  suited  for  baking  and  others  for  fermenting  purposes. 
The  fermenting  power  of  a  yeast  will  also  vary  with  the  character  of  the  liquid  in 
which  it  is  placed;  therefore,  when  a  yeast  is  found  to  be  particularly  suited  for  a 
special  purpose,  it  is  advisable  to  make  a  culture  of  it  so  that  a  start  or  seed  yeast  with 
the  desired  characteristics  will  always  be  available.  The  cultivation  of  a  yeast  does 
not  necessarily  improve  its  effectiveness,  but  simply  permits  the  reproduction  of  the 
desired  kind  of  yeast.  A  culture  yeast  with  known  characteristics  may  be  used, 
therefore,  with  more  certainty  of  uniformly  good  results  than  a  spontaneous  yeast. 

a  Acknowledgment  is  made  to  ft.  E.  Lee  for  assistance  in  the  preparation  of  this 
chapter. 

430 


POTATO  CULLS  AS  A  SOURCE  OF  INDUSTRIAL  ALCOHOL. 


25 


DEVELOPMENT  OF  A  START  YEAST. 

Yeast  culture  is  rather  difficult,  and  as  any  quantity  may  be  grown  from  one  start 
yeast,  it  is  best  to  obtain  the  initial  yeast  from  a  laboratory;  if  this  is  not  convenient, 
a  hop  yeast  may  be  grown,  or  as  a  last  resource  ordinary  compressed  baker’s  yeast 
may  be  used.  It  is  not  necessary,  for  fermentation  purposes,  to  separate  the  yeast 
from  the  liquid  in  which  it  is  grown,  but  the  entire  liquid,  together  with  the  yeast 
(known  as  the  “yeast  mash”),  may  be  put  into  the  liquid  which  is  to  be  fermented. 
It  requires  a  yeast  mash  of  about  2  to  3  per  cent  by  volume  of  the  main  mash  (as  the 
liquid  to  be  fermented  is  called)  to  carry  on  the  fermentation  properly,  so  that  the  start 
yeast  must  be  increased  or  grown  by  making  preliminary  yeast  mashes,  and  increas¬ 
ing  the  volume  ten  times  with  each  successive  mash  until  the  desired  quantity  is 
obtained.  These  mashes  are  prepared  exactly  like  the  one  now  to  be  described  and 
may  be  made  in  any  suitable  wood  or  copper  vessel. 

If  compressed  yeast  is  used  1  pound  will  be  sufficient  to  start  a  20-gallon  mash, 
and  if  culture  yeast  from  a  laboratory  is 
used  1  gallon  (which  is  the  amount  usually 
sold)  will  start  a  10-gallon  mash. 

PREPARATION  OF  A  SPONTA¬ 
NEOUS  HOP  YEAST. 

If  a  spontaneous  hop  yeast  is  to  be  used,  it 
must  be  obtained  in  the  following  manner: 

Boil  1  pound  of  hops  in  5  gallons  of  water 
for  fifteen  minutes;  strain  off  the  hops  and 
add  8  pounds  of  ground  barley  malt  to  the 
extract.  Allow  the  mixture  to  stand  about 
five  hours,  then  strain  it  through  a  fine 
brass  sieve  to  remove  all  the  particles  of 
grain,  cool  to  about  85°  F.,  and  place  in  a 
warm  room  and  hold  at  that  temperature. 

The  gravity  of  the  liquid  should  be  about 
20°  Balling.  In  about  ten  hours  fermenta¬ 
tion  will  begin  and  should  be  allowed  to  continue  until  the  gravity  has  fallen  to  6° 
or  8°  Balling.  The  resulting  spontaneous  or  hop  yeast  is  then  put  into  a  tin-lined 
copper  jug  and  kept  on  ice  or  in  a  cool  place  (preferably  in  running  water  or  at  the 
bottom  of  a  well)  at  a  temperature  never  exceeding  55°  F.,  under  which  conditions 
it  will  keep  indefinitely  and  a  start  yeast  will  be  obtainable  at  any  time.  The  jug  is 
made  absolutely  air  and  water  tight  and  provided  with  a  faucet  for  withdrawing  the 
yeast.  The  use  of  the  quantities  given  will  produce  about  2  gallons  of  yeast,  all  or 
part  of  which  may  be  used  to  start  a  yeast  mash  ten  times  the  volume  of  the  amount 
used. 

YEAST  MASHES. 

Yeast  will  grow  rapidly  in  a  liquid  containing  sugar  such  as  may  be  obtained  in  a 
potato  or  grain  mash  in  which  the  starch  of  these  materials  is  converted  into  sugar  by 
the  action  of  malt.  Rye  is  most  convenient  for  this  purpose,  as  the  malt  will  act  upon 
its  starch  without  the  preliminary  cooking,  which  is  necessary  in  the  case  of  potatoes. 
As  there  are  many  organisms  besides  yeast  that  feed  upon  sugar  and  are  not  only 
incapable  themselves  of  producing  alcohol,  but  are  also  decidedly  harmful  to  the 
development  of  the  yeast,  it  is  extremely  important  that  such  precautions  be  taken 
as  will  prevent  these  injurious  organisms  from  developing  in  the  mash,  and  that 
conditions  be  made  favorable  for  the  rapid  growth  of  the  yeast.  This  is  accomplished, 
410 


Fig.  10. — Growth  of  yeast  in  a  liquid  containing 
sugar  as  seen  under  the  microscope. 


26 


POTATO  CULLS  AS  A  SOURCE  OF  INDUSTRIAL  ALCOHOL. 


first,  by  allowing  the  mash  to  sour,  or  in  other  words  to  increase  its  natural  acidity, 
which  is  not  harmful  to  the  development  of  the  yeast  but  is  decidedly  so  to  most  other 
organisms;  second,  by  adding  a  sufficient  amount  of  yeast  to  carry  the  fermentation 
through  before  the  other  organisms  can  be  established.  These  operations  are  known 
as  souring  and  yeasting  the  mash.  The  details  of  preparing  a  grain  yeast  mash  are 
given  in  the  following  section: 

/ 

Preparation  of  a  Grain  Yeast  Mash. 

The  yeast  mash  is  prepared  in  a  wooden  tub  equipped  with  a  rake  for  stirring  and 
a  copper  coil  fitted  with  steam  and  water  connections  for  heating  and  cooling  the  mash 
as  shown  in  figure  1.  The  volume,  as  has  already  been  stated,  should  be  from  2  to  3 
per  cent  of  the  main  mash  to  be  fermented  and  10  times  that  of  the  yeast  mash  used 
to  start  it.  Equal  parts  by  weight  of  finely  ground  rye  meal  and  crushed  green  malt 
(or  ground  dried  malt)  are  added  to  water  in  the  proportion  of  1  quart  of  water  to  each 
pound  of  the  grain  used.  The  water  is  measured  into  the  tub  and  the  temperature 
raised  to  150°  F.  The  stirrer  is  then  started  and  the  rye  meal  allowed  to  run  in  slowly 
so  as  to  prevent  its  lumping.  The  addition  of  the  rye  will  cause  the  temperature  of 
the  mash  to  fall  to  about  140°  F.,  at  which  point  the  malt  is  added.  The  malt  is  allowed 
to  act  upon  the  starch  for  about  three  hours,  during  which  time  the  mash  is  stirred 
occasionally  and  the  temperature  is  gradually  raised  to  145°  F.  At  the  end  of  this 
time  the  formation  of  sugar  will  be  complete  and  the  gravity  of  the  mash  should  be 
about  20°  to  24°  Balling.  The  mash  is  then  ready  to  be  soured. 

Souring  the  mash. — It  has  been  found  that  acid  solutions  tend  to  suppress  organisms 
which  infect  starchy  materials.  This  is  especially  true  of  lactic  acid  and  as  this 
organism  is  always  present  in  potatoes  and  grain  the  acidity  of  the  mash  can  be 
increased  by  its  development  under  the  proper  conditions.  This  is  accomplished  by 
keeping  the  yeast  mash  at  130°  F.  for  forty-eight  hours,  at  the  end  of  which  time  the 
desired  acidity  will  be  obtained.  By  adding  a  start  sour  (that  is,  a  culture  of  lactic- 
acid  organisms)  to  the  yeast  mash  at  the  beginning  of  the  souring  period,  the  proper 
acidity  can  be  obtained  in  twenty-four  hours,  so  that  a  forty-eight  hour  period  is  only 
necessary  in  the  case  of  the  first  yeast  mash  or  if  a  new  sour  is  desired.  The  start  sour 
is  a  portion  of  a  previously  soured  yeast  mash  and  should  be  about  2  per  cent  of  the 
yeast  mash  to  which  it  is  added.  It  is  important  that  the  proper  temperature  be 
maintained  throughout  the  souring  period  in  order  to  prevent  the  growth  of  other  acid 
organisms  which  interfere  with  the  development  of  the  yeast. 

The  acidity  of  the  mash  (determined  as  explained  on  page  14)  at  the  beginning  of 
the  souring  period  is  called  its  natural  acidity  and  in  a  mash  prepared  as  described  will 
be  about  0.5  cc.  By  adding  a  start  sour  the  acidity  will  increase  in  twenty-four  hours 
to  about  2.5  or  3  cc,  when  the  start  sour  for  the  following  day’s  mash  is  withdrawn. 
An  acidity  of  2.5  or  3  cc  will  be  sufficient  to  suppress  all  undesirable  organisms  and 
will  not  interfere  with  the  proper  development  of  the  yeast.  Further  growth  of  the 
lactic  acid  organisms  which  have  now  produced  the  desired  acidity  must  be  prevented 
by  heating  the  mash  to  160°  F.  and  maintaining  this  temperature  for  twenty  minutes. 
The  mash  is  then  cooled,  by  passing  cold  water  through  the  coil,  to  a  temperature 
favorable  to  the  growth  of  the  yeast  (see  following  caption).  It  is  very  important  that 
the  cooling  be  done  as  quickly  as  possible  as  there  are  a  great  many  objectionable 
organisms  which  develop  at  the  warmer  temperatures. 

Yeasting  the  mash. — When  the  temperature  has  been  reduced  to  approximately  90° 
F.,  the  yeast  (about  10  per  cent  by  volume  of  the  mash)  is  added;  it  may  be  either  a 
preliminary  yeast  mash  or  a  quantity  of  mash  taken  from  the  previous  day’s  yeast 
mash,  the  former  being  the  case  when  the  distillery  is  just  being  put  into  operation,  or 
when  a  new  yeast  is  desired,  and  the  latter  when  the  plant  is  running  regularly.  The 
temperature  is  then  further  reduced  to  about  60°  to  70°  F.  This  final  temperature  is 
410 


POTATO  CULLS  AS  A  SOURCE  OE  INDUSTRIAL  ALCOHOL.  27 


called  the  “setting  temperature”  and  varies  with  the  volume  of  the  mash  and  the 
weather  conditions.  It  should  be  such  as  will  permit  the  immediate  growth  of  the 
yeast.  Gas  bubbles,  due  to  the  escape  of  carbonic-acid  gas,  appearing  on  the  surface 
of  the  mash  after  a  few  hours  will  indicate  that  the  yeast  has  become  active.  The  fer¬ 
mentation,  which  will  gradually  become  more  vigorous,  is  allowed  to  continue  for 
twenty-four  hours.  As  the  activity  of  the  yeast  increases,  the  temperature  of  the 
mash  will  rise  perceptibly,  but  it  should  not  be  allowed  to  go  above  90°  F.,  as  there 
will  then  be  danger  of  the  yeast  mash  becoming  infected  with  other  organisms,  such 
as  acetic  bacteria,  which  have  a  harmful  effect  on  the  fermentation. 

The  yeast  in  the  yeast  mash  should  be  active  and  vigorous  when  put  into  the  main 
mash  so  that  fermentation  will  begin  at  once.  The  yeast  remains  active  only  so  long 
as  there  is  sugar  present  for  its  growth,  consequently  the  yeast  mash  is  added  to  the 
main  mash  before  all  the  sugar  in  the  former  is  exhausted  or  when  its  gravity  has 
fallen  to  about  4°  or  5°  Balling.  If  it  is  allowed  to  fall  below  this  point  the  yeast  will 
become  less  vigorous  from  lack  of  food  and  delay  fermentation  of  the  main  mash. 

The  setting  temperature,  as  well  as  that  maintained  during  the  twenty-four-hour 
fermentation  period,  should  be  as  low  as  possible  and  still  permit  a  sufficient  growth 
of  the  yeast  to  cause  the  gravity  to  fall  to  4°  or  5°  Balling.  The  acidity  of  the  yeast 
mash  should  be  carefully  taken  after  the  souring  period,  or  rather  immediately  after 
the  mash  has  been  yeasted,  and  compared  with  that  of  the  mash  twenty-four  hours 
later,  namely,  after  the  fermentation  period.  Not  much  change  should  occur  as  any 
increase  would  indicate  the  presence  and  development  of  undesirable  acid  organisms, 
the  immediate  suppression  of  which  is  of  great  importance.  They  can  be  easily 
avoided  by  employing  only  the  proper  temperatures  and  keeping  the  tubs  sweet  and 
clean .  It  is  best  to  cover  the  tubs,  thoroughly  sterilize  them  with  live  steam,  and  scrub 
them  with  clean  water  after  each  use.  The  acidity  and  gravity  of  the  fermented 
mash  having  been  found  to  be  satisfactory,  a  quantity  amounting  to  about  10  per  cent 
by  volume  of  the  yeast  mash  to  which  it  is  to  be  added  is  removed  and  kept  at  a  tem¬ 
perature  below  55°  F.,  to  be  used  as  a  start  yeast  for  the  following  yeast  mash,  and  the 
rest  is  added  to  the  main  mash.  Summarizing  this  discussion,  it  is  seen  that  a  yeast 
mash  consists  of  a  selected  yeast  grown  in  a  suitable  mash  and  requires  about  fifty- 
one  hours  for  its  preparation,  of  which  three  hours  are  required  to  allow  the  malt  to  act 
upon  the  starch,  twenty-four  for  souring  the  mash,  and  twenty-four  for  growing  the 
yeast. 

Preparation  of  a  Potato  Yeast  Mash. 

The  selection  of  a  yeast  and  its  subsequent  development  in  the  mash  as  just  described 
will  be  applicable  to  either  a  grain  or  a  potato  distillery.  It  will  be  found  more  eco¬ 
nomical,  however,  in  the  latter  to  use  rye  in  the  first  two  or  three  yeast  mashes  and 
then  substitute  potatoes.  A  part  of  each  day’s  cooked  and  malted  potatoes  constitut¬ 
ing  the  main  mash  is  pumped  into  the  yeast  tub  and  one-half  pound  of  crushed  green 
malt  or  one-quarter  of  a  pound  of  dried  malt  is  added  for  each  gallon  of  potato  mash, 
this  additional  malt  being  added  to  serve  as  food  for  the  yeast.  It  is  not  necessary 
to  add  water.  To  the  malted  potato  yeast  mash  is  added  a  start  sour  taken  from  a 
previously  soured  potato  or  grain  mash,  and  after  twenty-four  hours  it  is  yeasted  by 
adding  a  start  yeast  taken  from  a  previous  grain  or  potato  yeast  mash.  Exactly  the 
same  operations  are  employed  and  the  same  temperatures  maintained  as  in  the  case  of 
the  grain  yeast  mash  just  described.  An  economical  potato-distilling  yeast  may  be 
obtained,  therefore,  by  the  growth  of  an  initial  start  yeast  in  a  grain  mash,  the  use  of 
grain  yeast  mashes  for  the  first  two  or  three  days’  operations,  and  the  subsequent  sub¬ 
stitution  of  potatoes  for  rye  in  the  yeast  mashes.  The  accompanying  schedule  out¬ 
lines  the  various  steps  necessary  in  the  building  up  and  daily  preparation  of  a  potato- 
distillery  yeast. 

410 


Working  schedule  for  operator  of  distillery. 


28 


POTATO  CULPS  AS  A  SOURCE  OF  INDUSTRIAL  ALCOHOL. 


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410 


Main  mash  No. 


Working  schedule  for  operator  of  distillery — Continued. 


30 


POTATO  CULLS  AS  A  SOURCE  OF  INDUSTRIAL  ALCOHOL. 


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POTATO  CULLS  AS  A  SOURCE  OF  INDUSTRIAL  ALCOHOL. 


31 


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32  POTATO  CULLS  AS  A  SOURCE  OF  INDUSTRIAL  ALCOHOL. 


ANALYTICAL  DATA. 

In  connection  with  the  experiments  on  potatoes  in  the  distillery 
certain  analytical  data  were  obtained  in  the  laboratory,  which  are 
of  considerable  interest,  as  they  show  the  composition  of  the  original 
material  used  and  also  of  the  by-products  obtained. 

COMPOSITION  OF  THE  WHOLE  POTATOES. 

In  the  first  table  are  given  the  analytical  results  obtained  for  the  various  lots  of 
potatoes  used.  A  complete  analysis  of  these  potatoes  was  made  in  order  to  compare 
their  composition  with  that  of  the  mash  at  its  various  stages.  In  distillery  practice, 
however,  the  chief  determinations  of  value  are  the  sugar  and  starch,  as  these  con¬ 
stituents  determine  the  value  of  potatoes  for  the  manufacture  of  alcohol. 

Special  attention  is  called  to  the  analysis  of  the  potatoes  used  in  mash  No.  31. 
These  were  small  unmarketable  culls,  averaging  not  more  than  1  inch  in  diameter, 
and  were  found  to  contain  14.5  per  cent  of  starch,  which  is  as  much  and  more  than  was 
found  in  some  of  the  other  potatoes  that  were  of  a  size  and  grade  ordinarily  used  for 
eating  purposes.  The  analyses  of  the  potatoes  were  also  calculated  to  a  moisture-free 
basis  in  order  that  the  composition  of  their  dry  material  might  be  readily  compared 
with  that  of  the  fermented  mash  or  slop. 


Analysis  of  potatoes. 

BASED  ON  ORIGINAL  MATERIAL. 


Mash. 

Total 

solids. 

Ash. 

Protein 
(N  X 
6.25.) 

Ether 

ex¬ 

tract. 

Sugars  as  dex¬ 
trose. 

Starch. 

Crude 

fiber. 

Nitro¬ 

gen- 

free. 

Before 

inver¬ 

sion. 

After 

inver¬ 

sion. 

By 

dias¬ 

tase. 

Calcu¬ 
lated 
from 
solids  by 
Maerck- 
er’s 
table. 

Per  ct. 

Per  ct. 

Per  ct. 

Per  ct. 

Per  ct. 

Per  ct. 

Per  ct. 

Per  ct. 

Per  ct. 

Per  ct. 

No.  14 . 

22.  70 

2.  45 

0. 10 

0.39 

0. 39 

16.4 

16.9 

0.53 

2. 83 

No.  15 . 

21.30 

.64 

.64 

15.8 

15.5 

No.  16 . 

21.57 

.32 

.40 

15.4 

15.8 

No.  17 . 

21.90 

.46 

.46 

16.2 

16.2 

No.  19 . 

20.50 

0.85 

2.  02 

.03 

.80 

1.06 

14.4 

14.7 

.51 

1.63 

No.  21 . 

20.38 

.80 

2.31 

.03 

.72 

.91 

13.7 

14.5 

.50 

2. 13 

No.  22 . 

20.  62 

.80 

2.  33 

.04 

Trace 

Trace 

13.9 

14.9 

.50 

3.05 

No.  23 . 

19.  96 

.99 

1.75 

.02 

.27 

.41 

14.0 

14.2 

.37 

3.  42 

No.  25 . 

20.00 

.92 

2.08 

.09 

.26 

.38 

13.6 

14.3 

.38 

2.  55 

No.  26 . 

21.70 

1.08 

2. 19 

.08 

.20 

.20 

15.2 

16.0 

.42 

2.53 

No.  27 . 

21.33 

1.05 

2. 19 

.08 

.18 

.18 

14.6 

15.5 

.49 

2.75 

No.  29 . 

19.60 

1.02 

2. 13 

.09 

Trace 

Trace 

13.7 

13.8 

.41 

2.  25 

No.  30 . 

19.20 

1.01 

2.  04 

.08 

Trace 

Trace 

13.7 

13.5 

.49 

1.88 

No.  31 . 

20.20 

1.10 

1.58 

.06 

.43 

.43 

14.1 

14.5 

.61 

2.  32 

Average . 

20.  78 

.96 

2.09 

.06 

.33 

.39 

14.6 

15.0 

.47 

2. 19 

MOISTURE-FREE  BASIS. 


No.  14 . 

10.  79 

0.44 

1.72 
3.00 
1.48 
2. 10 
3.90 
3.  53 
Trace 
1.35 
1.30 
.92 
.84 
Trace 
Trace 

2. 13 

1.72 
3.00 
1.85 
2. 10 
5. 17 
4.  47 
Trace 

2. 05 
1.90 
.92 
.84 
Trace 
Trace 

2. 13 

72.25 
74. 18 
71.39 
73. 97 
70. 24 
67. 22 
67.41 
70. 14 
68.00 
70. 04 
68.45 
69.89 
71.35 
69.80 

2.33 

12.  46 

No.  15 . 

No.  16 . 

No.  17 . 

No.  19 . 

4. 15 
3. 93 
3.88 
4. 96 
4.66 
4.98 
4.92 
5.20 
5.  26 
5.45 

9.85 
11.33 
11.29 
8.77 
10.40 
10.90 
10.  26 
10.86 
10.62 
7.82 

.15 
.15 
.19 
.  10 
.45 
.36 
.37 
.46 
.42 
.29 

2. 49 
2.  45 
2.42 
1.85 
1.90 
1.  94 
2.29 
2.09 
2.55 
3.02 

7.95 
10.  45 
14.  79 
17.  13 
12.  75 
11.65 
12.89 

11.47 
9.  79 

11.48 

No.  21 . 

No.  22 . 

No.  23 . 

No.  25 . 

No.  26 . 

No.  27 . 

No.  29 . 

No.  30 . 

No.  31 . 

Average . 

4.69 

10. 06 

.29 

1.59 

1.88 

70.  35 

2.  26 

10. 55 

Purchase  on  Basis  of  Starch  Content. 

The  results  given  in  the  table  indicate  clearly  that  it  will  be  necessary  to  buy  pota¬ 
toes  for  making  alcohol,  not  by  weight,  but  on  the  basis  of  their  starch  content.  The 
difference  in  the  value  of  potatoes  for  alcohol-making  is  illustrated  by  comparing  the 
starch  content  of  the  potatoes  of  mash  No.  14,  i.  e.,  16.9  per  cent,  with  that  of  mash 
410 


POTATO  CULLS  AS  A  SOURCE  OF  INDUSTRIAL  ALCOHOL. 


33 


No.  30,  i.  e.,  13.5  per  cent.  In  a  ton  of  potatoes  containing  16.9  per  cent  of  starch 
there  would  be  338  pounds  of  starch,  while  in  the  same  amount  of  potatoes  containing 
13.5  per  cent  of  starch  there  would  be  only  270  pounds,  a  difference  of  68  pounds. 
Since  1  pound  of  starch  will  yield  0.079  gallon  of  90  per  cent  alcohol,  the  68  pounds 
would  yield  5.37  gallons,  which  at  40  cents  a  gallon  would  be  worth  $2.15.  That  is, 
the  first  lot  of  potatoes  would  be  worth  $2.15  more  per  ton  for  the  production  of  alcohol 
than  the  second  lot.  It  can  be  readily  seen  that  success  or  failure  might  depend  on 
the  basis  upon  which  the  potatoes  were  bought. 

Simple  Method  of  Determining  Starch. 

To  establish  an  accurate  but  shorter  method  than  that  of  actual  analysis  for  obtaining 
the  starch  content  of  potatoes,  a  determination  of  the  solids  by  drying  at  100°  C. 
was  made  on  14  samples  and  from  it  the  starch  content  was  calculated  by  Maerck- 
er’s  table.0  This  calculation  gave  15  per  cent  of  total  starch,  while  the  average 
result  of  the  14  analyses  was  14.99  per  cent  of  sugar  and  starch,  proving  conclusively 
that  for  factory  practice  in  buying  potatoes  on  the  starch  content,  this  method  of  deter¬ 
mination  is  entirely  satisfactory.  Whether  the  still  more  simple  method  of  determin¬ 
ing  the  specific  gravity  of  the  potatoes  is  sufficiently  accurate  has  not  yet  been  decided. 
The  determination  of  solids  requires  some  chemical  knowledge,  while  the  apparatus 
for  obtaining  the  starch  content  from  the  specific  gravity  has  been  so  simplified  as  to 
give  a  Vory  rapid  and  easy  method,  and  if  accurate  enough  it  will  have  many  ad¬ 
vantages  ever  the  other  methods  because  of  the  fact  that  a  person  without  any  chem¬ 
ical  training  can  use  it. 

ANALYSIS  OF  POTATO  SKINS. 

The  composition  of  the  material  separated  by  the  peel  extractor,  consisting  of  the 
skin  and  fibrous  or  woody  portions  of  the  potato,  which  were  not  disintegrated  during  the 
cooking  process,  is  shown  in  the  following  table.  The  results  obtained  are  extremely 
interesting,  showing  how  much  richer  this  material  is  in  proteins  and  how  much 
poorer  in  starch  than  the  whole  potato.  This  illustrates  the  well-known  fact  that  the 
protein  of  the  potato  is  in  a  layer  close  to  the  skin. 

Analysis  of  potato  skins  ( extracted  from  the  mash  by  peel  extractor). 

BASED  ON  ORIGINAL  MATERIAL. 


Mash. 

Total 

solids. 

Ash. 

Protein 
(NX  6.25) 

Ether 

extract. 

Sugar  as 
dextrose. 

Starch  by 
diastase. 

Crude 

fiber. 

Nitrogen- 

free. 

Percent¬ 
age  of 
total  po¬ 
tatoes. 

Per  ct. 

Per  ct. 

Per  cent. 

Per  ct. 

Per  cent. 

Per  cent. 

Per  ct. 

Per  cent. 

No.  19 . 

32.2 

1.99 

6. 10 

0.  96 

1.83 

0.  90 

8. 17 

12.  25 

No.  21 . 

32.9 

1.74 

10.  80 

.81 

.20 

2.  40 

7.  53 

9.  42 

No.  22 . 

26.  2 

1.39 

7.52 

.73 

.21 

1.70 

5.  55 

9. 10 

2.  49 

No.  23 . 

35.0 

2. 15 

6.  76 

.76 

.35 

2. 18 

6.  70 

16. 10 

1.93 

No.  25 . 

30.7 

1.86 

5.  99 

.75 

.39 

1.70 

5.  65 

14.  36 

1.94 

No.  26 . 

27.9 

1.90 

5.  59 

.55 

.33 

2.  89 

4.63 

12. 01 

2.02 

No.  27 . 

24.8 

1.66 

5.  20 

.55 

.28 

3.00 

5. 18 

8.  93 

2.  30 

No.  29 . 

24.8 

1.92 

5.  24 

.63 

.24 

2.  43 

5.  38 

8.  96 

1.72 

No.  30 . 

22.  1 

1.74 

4.58 

.46 

.28 

2.50 

4.  49 

8.  05 

2.  33 

No.  31 . 

23.  6 

1.65 

3.92 

.66 

.  12 

2.  90 

4.  82 

9.53 

3.69 

Average . 

28.0 

1.81 

6. 13 

.71 

.43 

2.26 

5.  79 

10.  87 

2.30 

MOISTURE-FREE  BASIS. 


Mash. 

Total 

solids. 

Ash. 

Protein 
(NX  6.25) 

Ether 

extract. 

Sugar  as 
dextrose. 

Starch  by 
diastase. 

Crude 

fiber. 

Nitrogen- 

free. 

Percent¬ 
age  of 
total  po¬ 
tatoes. 

No.  19 . 

Per  ct. 

Per  ct. 
6. 18 
5. 29 

5.  29 
6.14 
6.06 

6.  79 
6.70 
7.75 
7.90 
7.00 

Per  cent. 

18.  94 
32.  83 
28.  65 
19.31 

19.  51 
19.98 

20.  96 
21. 12 
20.  76 
16.  63 

Per  ct. 
2.  98 
2.47 
2.77 
2.17 
2.44 
1.97 
2.23 
2.52 
2.09 
2.82 

Per  cent. 
5.  67 
.59 
.82 
.99 
1.27 
1.19 
1.15 
.96 
1.26 
.53 

Per  cent. 
2.  79 
7.29 
6.  48 
6.  23 
5.53 
b  10.  33 
b  12. 10 
b  12. 11 
b  11.  30 
b  12.  30 

Per  ct. 
25. 37 
22.  89 
21. 15 
T9. 14 
18.  40 
16.55 

20.  91 

21.  69 
20.  35 
20.  46 

Per  cent. 
38.  07 
28.64 

34. 84 
46.  02 
46.  79 
43.19 
35.  95 

33.85 
36. 34 
40.  26 

No.  21 . . . 

No.  22 . 

No.  23 . 

No.  25. . . 

No.  26 . 

No.  27... 

No.  29 

No.  30. 

No.  31 . 

Average . 

6.  51 

21.87 

2.55 

1.44 

8.  65 

20.  69 

38.  40 

a  Handlruch  der  Spiritusfabrication,  p.  17C.  b  Sample  taken  before  complete  malting. 

410 


34 


POTATO  CULLS  AS  A  SOURCE  OF  INDUSTRIAL  ALCOHOL. 


The  average  of  the  analyses,  calculated  to  a  water-free  basis,  shows  that  the  skins 
contained  21.87  per  cent  of  protein  and  8.65  per  cent  of  starch  as  compared  with  10.06 
per  cent  of  protein  and  70.31  per  cent  of  starch  in  the  whole  potato.  The  skins  are 
also  much  richer  in  fat.  This  shows  that  weight  for  weight  the  skins  are  much  more 
valuable  as  a  cattle  food  than  the  whole  potato.  On  the  other  hand,  the  loss  of  alcohol- 
producing  material  by  separating  the  skins  from  the  mash  is  very  slight,  as  they 
average  only  2.3  per  cent  of  the  whole  potato. 

COMPOSITION  OF  THE  POTATO  SLOP. 

The  following  table,  giving  the  composition  of  the  slop  or  residue  of  the  mash  after 
the  alcohol  has  been  removed,  is  exceedingly  interesting  as  it  shows  the  value  of  this 

important  by-product  as  a  cattle  food : 

« 

Analysis  of  potato  slop. 

BASED  ON  ORIGINAL  MATERIAL. 


Mash. 

Total 

solids. 

Ash. 

Protein 

(NX6.25). 

Ether 

extract. 

Sugar  as 
dextrose. 

Starch. 

Crude 

fiber. 

Nitrogen- 
free  ex¬ 
tract 

Per  cent. 

Per  cent. 

Per  cent. 

Per  cent. 

Per  cent. 

Per  cent. 

Per  cent. 

Per  cent. 

No.  15 . 

6.  90 

2.26 

0. 17 

0. 29 

0.70 

3.  40 

No.  21 . 

7.17 

0.  67 

1.97 

0.04 

.21 

.15 

.52 

3.61 

No.  22 . 

5.80 

.69 

1.91 

.08 

.06 

.10 

.58 

<  2.38 

No.  23 . 

5. 90 

.72 

1.68 

.04 

.14 

.27 

.46 

2.59 

No.  25 . 

7.22 

.84 

2.  05 

.01 

.17 

.16 

.47 

3.52 

Average . 

6.59 

.73 

1.97 

.04 

.15 

.19 

.55 

2.  96 

MOISTURE-FREE  BASIS. 


No.  15 . 

32.  75 

2.  46 

4.20 

10. 14 

50.  45 

No.  21 . 

9. 30 

27.  47 

0.56 

2.93 

2. 10 

7.25 

50.  39 

No.  22 . 

11.90 

32. 93 

1.38 

1.34 

1.  72 

10.  00 

40.  73 

No.  23 . 

12.20 

28.  47 

.68 

2.  37 

4.58 

7.79 

43.  91 

No.  25 . 

11.63 

28.  39 

.14 

2.35 

2.  22 

6.50 

48.  77 

A  verage . 

11.26 

30.  00 

.69 

- - 

2.  29 

2.98 

6.  54 

46. 24 

A  comparison  of  the  composition  of  the  dry  material  of  the  whole  potato,  the  potato 
skins,  and  the  slop,  using  the  averages  of  the  three  preceding  tables  is  here  made: 


Comparative  average  analyses  of  potatoes ,  the  shins,  and  the  slop. 


Material. 

Ash. 

Protein 
(NX  6.25). 

Ether  ex¬ 
tract  (fat). 

Sugar  as 
dextrose. 

Starch. 

Crude 

fiber. 

Nitrogen- 
free  ex¬ 
tract. 

Potato . 

Potato  skins . 

Slop . 

Per  cent. 
4.  39 
6.  51 
11.26 

Per  cent. 
10. 06 
21.87 
30.00 

Per  cent. 
0.  29 
2.55 
.69 

Per  cent. 
1.59 
1.44 
2.29 

Per  cent. 
70. 35 
8.  65 
2. 98 

Per  cent. 
2.26 
20.69 
6.  54 

Per  cent. 
10.55 
38.  40 
46. 24 

This  table  shows  that  the  dry  substance  in  the  slop  is  very  different  in  composition 
from  the  potato  itself,  being  a  more  highly  nitrogenous  food.  The  great  increase  in 
the  amount  of  protein  as  compared  with  the  total  dry  substance  in  the  slop  is,  of 
course,  due  to  the  fermentation  of  the  starch  and  sugar,  resulting  in  a  concentration 
of  the  nitrogenous  material.  The  actual  value  of  slop  as  a  food  for  cattle  is  discussed 
under  the  following  caption. 


SLOP  FEEDING.0 

GENERAL  DISCUSSION. 

Any  scheme  for  the  operation  of  agricultural  distilleries,  whether 
small  or  large,  should  provide  for  the  utilization  of  the  by-product 

a  This  chapter,  with  the  exception  of  the  formulas  for  rations,  was  prepared  by 
H.  E.  Sawyer. 

410 


POTATO  CULLS  AS  A  SOURCE  OF  INDUSTRIAL  ALCOHOL. 


35 


known  as  “slop.”  This  is  the  residuum  remaining  after  the  alcohol 
and  a  small  amount  of  water  have  been  boiled  off  from  the  fermented 
distillery  mash;  and  it  contains,  dissolved  or  suspended  in  the  remain¬ 
ing  liquid  of  the  mash,  all  of  the  constituents  of  the  materials  em¬ 
ployed  except  that  portion  of  the  sugars  and  starch  which  was  con¬ 
verted  into  alcohol  during  the  fermentation.  This  slop  has  been 
found,  both  in  this  country  and  abroad,  to  be  a  feeding  stuff  of  high 
value  and  should  be  fed  to  the  stock  on  the  farm  that  furnishes  the 
raw  materials  used  in  the  distillery.  In  this  way  its  full  utilization 
can  be  secured.  First,  through  the  production  of  flesh,  milk,  or  energy 
in  the  stock  to  which  it  is  fed;  and,  second,  by  returning  to  the  soil 
in  the  form  of  manure  those  necessary  elements  of  plant  food  which 
were  abstracted  during  the  production  of  the  potatoes  or  other  raw 
materials. 

The  chemical  composition  of  feeding  stuffs  and  the  special  functions 
of  their  different  constituents  are  discussed  fully  in  various  accessible 
publications  which  deal  with  the  principles  and  practice  of  cattle  feed¬ 
ing. a  Therefore,  it  will  be  assumed  in  the  following  paragraphs  that 
the  reader  is  familiar  with  the  terms  in  which  the  composition  of  such 
materials  is  stated — such,  for  example,  as  moisture,  ash,  protein,  fat, 
carbohydrates,  sugars,  starch,  pentosans,  and  fiber — and  with  the 
significance  of  such  expressions  as  coefficient  of  digestibility,  cal¬ 
orific  value,  production  value,  and  nutritive  ratio,  which  it  will 
be  necessary  to  use  in  discussing  the  nutritive  value  of  slop  and  the 
way  in  which  it  should  be  used  as  part  of  a  properly  balanced  daily 
ration. 

COMPARISON  OF  GRAIN  AND  POTATO  SLOPS. 

Since  the  chemical  constituents  of  distillery  slop  are  essentially  identical  with  those 
of  the  distiller’s  raw  materials,  save  for  a  diminution  in  the  proportions  of  fermentable 
carbohydrates,  and  since  different  kinds  of  raw  material  vary  greatly  in  their  typical 
compositions,  it  follows  that  the  composition  and  the  nutritive  value  of  slop  will  be 
dependent  on  the  selection  of  raw  materials  and  will  vary  considerably  according  to 
the  nature  of  the  latter.  This  is  well  illustrated  by  the  following  examples,  drawn 
from  the  records  of  the  Department’s  experimental  distillery  for  the  season  of  1909. 

Example  No.  1. 

Grain  mash;  fermentation,  Serial  No.  4. 

Mash  contained  1,680  pounds  of  maize,  100  pounds  of  rye,  and  350  pounds  of  dry 
malt,  all  of  the  rye  and  100  pounds  of  the  malt  being  used  in  preparing  the  yeast  mash. 
The  volume  of  the  main  mash,  about  1,000  gallons,  yielded  175  proof  gallons  of  alcohol 
and  about  1,000  gallons  of  slop. 

a  The  Feeding  Value  of  Cereals:  U.  S.  Dept.  Agr.,  Bureau  of  Chemistry,  Bui.  120. 
The  Feeding  of  Farm  Animals:  U.  S.  Dept.  Agr.,  Farmers’  Bui.  22.  The  Computa¬ 
tion  of  Rations  for  Farm  Animals  by  the  Use  of  Energy  Values:  U.  S.  Dept.  Agr., 
Farmers’  Bui.  346. 


410 


36  POTATO  CULLS  AS  A  SOURCE  OF  INDUSTRIAL  ALCOHOL. 

Example  No.  2. 

Potato  mash;  fermentation,  Serial  No.  31. 

Mash  contained  4,760  pounds  of  potatoes  and  115  pounds  of  green  malt,  320  pounds 
of  the  potatoes  and  25  pounds  of  the  malt  being  used  in  making  the  yeast  mash.  The 
volume  of  the  main  mash,  about  625  gallons,  yielded  101.4  proof  gallons  of  alcohol 
and  about  625  gallons  of  slop. 

The  composition  of  the  raw  materials  used  in  these  two  mashes  was  as  follows: 


Chemical  composition  of  raw  materials  used  in  mashes. 


Materials. 

Moisture. 

Protein. 

Fat. 

Nitrogen- 

free 

extract. 

Fiber. 

Ash. 

Vlaize  . 

Per  cent. 
11.3 
9.4 

Per  cent. 
8.9 

Per  cent. 
4. 1 

Per  cent. 
72.4 

Per  cent. 
1.  9 

Per  cent. 
1.  4 

Rye  . 

10.7 

1.9 

74.0 

1.9 

2. 1 

Dry  malt . 

7.3 

11.3 

2.0 

71.2 

5.6 

2.6 

Green  malt . 

42.0 

12.3 

.8 

35.9 

6. 1 

2.9 

Potatoes . 

79.8 

1.6 

.  1 

16.9 

.6 

1.0 

The  1,000  gallons  comprising  mash  No.  1  contained  2,130  pounds  of  air-drv  grain, 
representing  1,903  pounds  of  dry  substance  of  the  following  composition: 


Pounds. 

Protein .  199.5 

Fat .  77.6 

Nitrogen-free  extract .  1,  539.  0 

Fiber .  52.  9 

Ash .  34.0 


Total .  1,903.0 


It  may  be  assumed  that  every  proof  gallon  of  alcohol  obtained  from  this  mash  repre¬ 
sented  the  decomposition  of  6.4  pounds  of  nitrogen-free  extract,  calculated  as  starch. 
As  175  gallons  were  produced,  it  will  be  seen  that  1,120  pounds  of  solids  in  the  form 
of  nitrogen-free  extract  must  have  disappeared  during  the  fermentation,  leaving  in 
the  slop  419  pounds  of  nitrogen-free  extract  and  783  pounds  of  dry  solids,  equivalent 
to  41.1  per  cent  of  the  total  dry  solids  of  the  materials  mashed. 

In  the  case  of  example  No.  2,  625  gallons  of  mash  contained  4,760  pounds  of  potatoes 
and  115  pounds  of  green  malt,  representing  1,028  pounds  of  total  dry  substance,  divided 
as  follows: 

Pounds. 


Protein .  90.4 

Fat .  5.7 

Nitrogen-free  extract .  845.  7 

Fiber .  35.  5 

Ash .  50.9 


Total .  1,028.2 

This  mash  yielded  101.4  proof  gallons  of  alcohol,  consuming  6.4  pounds  of  starch 
per  gallon;  therefore  649  pounds  of  starch  must  have  disappeared  during  fermenta¬ 
tion,  leaving  197  pounds  of  nitrogen-free  extract  and  379  pounds  of  total  dry  substance 
in  the  slop,  equivalent  to  37  per  cent  of  the  original  dry  substance  in  the  mash. 

A  comparison  of  the  composition  of  the  two  slops  is  facilitated  by  the  conversion  of 
the  amounts  of  the  several  constituents  into  percentages  on  the  dry  basis,  as  shown  in 
the  following  tabulation: 

410 


POTATO  CULLS  AS  A  SOURCE  OF  INDUSTRIAL  ALCOHOL. 


37 


Percentage  composition  of  grain  and  potato  slops. 
[Calculated  to  dry  basis.] 


Determinations. 

Grain 

slop. 

Potato 

slop. 

Protein . 

Per  cent. 

25.5 
9.9 

53.5 
6.7 
4.4 

Per  cent. 
23.9 
1.5 
52.0 
9.3 
13.3 

Fat . 

Nitrogen-free  extract . 

Fiber . 

Ash . 

Total . 

ion  n 

inn  n 

These  figures  show  a  marked  difference  between  the  two  slops,  the  potato  slop  being 
8.4  per  cent  lower  in  fat  and  8.9  per  cent  higher  in  ash  than  that  from  the  grain.  A 
further  difference,  not  shown  by  the  table,  exists  in  the  nature  of  the  various  nitrog¬ 
enous  constituents  which  are  grouped  under  the  term  “protein.”  About  94  per  cent 
of  the  nitrogen  compounds  present  in  maize  slop  are  of  true  protein  nature,  having  a 
high  nutrient  value,  whereas  only  71  per  cent  of  the  nitrogen  of  the  potato  slop  is  in 
the  form  of  protein,  the  balance  being  present  as  amido  compounds  which  are  practi¬ 
cally  worthless  as  food.  In  two  respects,  therefore,  potato  slop  is  inferior  to  that 
obtained  from  grain,  it  is  deficient  in  fat  and  in  true  protein.  Notwithstanding  this, 
however,  it  is  a  feeding  stuff  of  decided  value. 

COEFFICIENTS  OF  DIGESTIBILITY. 

To  estimate  the  feeding  value  of  slop  there  must  be  known,  in  addition  to  the 
composition  of  its  dry  substance,  the  extent  to  which  its  several  constituents  can  be 
digested  and  utilized  by  the  animals  to  which  it  may  be  fed.  This  factor,  which  is 
called  the  coefficient  of  digestibility,  varies  with  the  nature  of  the  constituents  and 
with  the  kind  of  animals  feda  and  can  be  obtained  only  by  very  careful  feeding 
experiments,  such  as  have  been  conducted  by  Kellner  at  the  Mockern  experiment 
station.  The  values  given  are  based  on  his  results. & 


Coefficients  of  digestibility  of  slop. 


Constituents. 

Maize. 

Potatoes. 

Protein . 

Per  cent. 
65 
95 
71 
50 

Per  cert. 
50 

95 

71 

20 

Fat . 

Extract . 

Fiber . 

With  the  aid  of  these  factors,  it  is  ascertained  that  100-pound  portions  of  dry  sub¬ 
stance  from  maize  slop  and  potato  slop  contain  respectively  the  following  amounts 
of  digestible  nutrients: 

Weights  of  digestible  nutrients  in  100  pounds  of  dry  slop  substance. 


Digestible  constituents. 

Maize 

slop. 

Potato 

slop. 

Protein . 

Pounds. 

16.6 

9.4 
38.0 

3.4 

Pounds. 

U-9 

1.4 

36.9 

1.9 

Fat . 

Extract . 

Fiber . 

Total . 

67.4 

52.1 

a  U.  S.  Dept.  Agr.,  Bureau  of  Chemistry  Bui.  120,  p.  8. 

b  Keliner,  Die  Brniihrung  der  landwirthschaftlichen  Nutztiere,  1905,  pp.  5C4-570. 

410 


38  POTATO  CULLS  AS  A  SOURCE  OF  INDUSTRIAL  ALCOHOL. 


PRODUCTION  VALUES. 

By  the  use  of  another  set  of  factors  a  it  is  possible  to  calculate  approximately  what 
weight  of  flesh  will  be  gained  by  cattle  to  which  definite  rations  of  slop  solids  are  being 
fed.  The  most  important  of  these  are  given  in  the  table. 


Production  value  of  food  nutrients. 


Nutrients. 

Flesh  gained 
by  mature  fat¬ 
tening  oxen 
per  100  pounds 
of  nutrient. 

Protein . 

Pounds. 

23.5 

52.6 
24.8 

Fat . 

Extract  and  fiber . 

The  weights  of  the  individual  nutrients  in  100  pounds  of  dry  slop  substance,  mul¬ 
tiplied  by  the  appropriate  factors  from  the  foregoing  table,  give  the  flesh-producing 
capacities  of  the  amounts  of  the  several  nutrients  present;  and  the  sum  of  these  prod¬ 
ucts  indicates  the  flesh-producing  value  of  the  100  pounds  of  slop  solids.  In  the  case 
of  the  two  slops  under  discussion  these  values  will  be  as  follows: 


Flesh-producing  capacities  of  100  pounds  of  slop  solids. 


Nutrients. 

Maize 

slop. 

Potato 

slop. 

Protein . 

Pounds. 

3.9 

4.9 
10.3 

Pounds. 

2.8 

.7 

9.6 

Fat . 

Carbohydrates . 

Total . 

19.1 

13.1 

Knowing  the  weight  of  the  solids  in  a  single  gallon  of  slop,  the  flesh -producing 
capacity  of  any  volume  of  the  slop  can  be  calculated  by  these  values.  Thus  a  gallon 
of  maize  slop,  which  contains  0.783  pound  of  dry  solids,  will  have  a  flesh-producing 
capacity  of  0.15  pound  (0.783  X  0.191).  The  corresponding  value  for  potato  slop,  con¬ 
taining  0.606  pound  of  dry  substance  per  gallon,  will  be  0.08  pound  (0.606  X  0.131). 
Thus,  it  is  seen  that  the  feeding  value  of  this  maize  slop  is  approximately  twice  that 
of  the  potato  slop  and  that  2  gallons  of  the  latter  would  have  to  be  fed  to  provide  the 
amount  of  nutrients  contained  in  a  single  gallon  of  the  former. 

NUTRITIVE  RATIO. 

In  addition  to  the  production  values,  which  have  just  been  discussed,  another  point 
relating  to  the  nutrient  qualities  of  slop  remains  to  be  considered,  namely,  the  balance 
between  the  nitrogenous  and  non-nitrogenous  constituents.  This  relation,  which  is 
called  the  “nutritive  ratio,”  expresses  the  proportion  between  those  elements  of  a  food 
which  are  fitted  respectively  to  produce  muscular  tissues  on  the  one  hand  and  fat, 
body  heat,  and  energy  on  the  other.  This  ratio  is  obtained  numerically  by  multiply¬ 
ing  the  percentage  of  digestible  fat  by  2.25,  adding  the  product  to  the  aggregate  percent¬ 
age  of  digestible  carbohydrates,  and  dividing  the  sum  by  the  percentage  of  digestible 
protein.  If  the  ratio  is  small  (1:3  to  1:  7)  it  is  termed  “  narrow.”  If  it  is  large  (1:  8  to 
1: 12)  it  is  termed  “broad.”  Maize  is  an  example  of  a  broad  ratio  and  oats  of  a  narrow 
one,  the  former  being  a  heat-producing  food  with  a  ratio  of  1:12.3,  and  the  latter  a 
tissue-forming  food  whose  ratio  is  1: 5.8.  b 

a  U.  S.  Dept.  Agr.,  Bureau  of  Chemistry  Bui.  120,  p.  14. 
b  U.  S.  Dept.  Agr.,  Bureau  of  Chemistry  Bui.  120,  p.  16. 


410 


POTATO  CULLS  AS  A  SOURCE  OF  INDUSTRIAL  ALCOHOL. 


39 


The  significance  of  the  nutritive  ratio  is  this:  Fats  and  carbohydrates  are  not  adapted 
to  the  formation  of  lean  meat,  which  is  distinctively  a  nitrogenous  tissue;  and  at  the 
same  time  protein  is  not  a  good  energy-producing  food,  although  a  certain  amount  of  it 
is  indispensable  in  any  ration  in  order  to  provide  for  the  formation  or  renewal  of  mus¬ 
cular  tissue.  Therefore,  very  broad  or  very  narrow  nutritive  ratios,  corresponding 
to  excessive  proportions  of  carbohydrates  or  protein,  are  not  desirable  in  a  steady 
course  of  feeding.  The  ratios  in  the  two  slops  which  are  under  discussion  are  1:3.8  for 
the  maize  and  1:3.5  for  the  potato.  Both  are  excessively  narrow,  and  it  would  be 
imperative  to  feed  either  material  in  conjunction  with  other  foods  rich  in  fats  and 
carbohydrates. 

RATIONS  CONTAINING  SLOP. 

The  large  proportion  of  water  contained  in  all  slop  has  an  important  bearing  in 
determining  the  amount  of  slop  solids  which  can  be  fed  to  any  animal  in  one  day.  It 
has  been  customary  in  this  country,  where  cattle  have  been  fed  with  slop  in  sheds  on 
the  grounds  of  large  whisky  and  alcohol  distilleries  and  not  on  the  farm,  to  allow  each 
bullock  daily  the  volume  of  slop  corresponding  to  a  bushel  of  the  grain  mashed.  In 
other  words,  a  distillery  mashing  1,000  bushels  daily  will  distribute  its  slop  among 
1,000  head  of  cattle.  Reduced  to  volume,  this  would  be  equivalent  to  about  30  gallons 
per  head  per  day.  This  amount  is  excessive,  even  when  fed  with  considerable  quan¬ 
tities  of  hay  and  other  roughage,  as  is  shown  by  the  flabbiness  of  the  stock  and  the 
liquid  character  of  their  manure.  The  injurious  effect  of  the  slop  when  fed  excessively, 
as  heretofore  in  this  country,  is  liable  in  the  case  of  milch  cows  to  result  in  dangerous 
contamination  of  their  milk  through  the  great  difficulty  of  keeping  their  hind  quarters 
clean. 

In  Germany,  where  slop  feeding  has  been  practiced  very  successfully  on  the  basis 
of  careful  investigations  at  the  agricultural  experiment  stations,  it  is  customary  to  feed 
much  smaller  volumes.  According  to  Maercker,  it  is  allowable  to  give  from  18  to  20 
gallons  per  head  per  day  in  fattening  oxen  weighing  from  1,300  to  1,400  pounds.  More 
than  this  amount  has  been  found  injurious.  Milch  cows  should  not  receive  more  than 
16  gallons  daily.  It  is  necessary  to  feed  the  slop  as  hot  as  possible,  and  since  it  is 
especially  susceptible  to  bacterial  decomposition  it  should  also  be  fed  when  fresh. 

Investigations  are  needed  in  this  country  to  determine  the  composition  of  rations, 
suited  to  American  conditions,  in  which  potato  slop  takes  its  proper  place.  Pending 
the  institution  of  such  studies,  the  following  German  formulas  taken  from  Maercker 
will  serve  to  show  the  make-up  of  balanced  rations,  for  different  purposes,  which  have 
proved  satisfactory  abroad. 

Rations  for  young  oxen. 

Four  and  five-tenths  pounds  of  digestible  protein  and  26.5  pounds  of  starch  value 
per  day  per  2,200  pounds  live  weight. 

No.  1.  Basal  ration:  88  pounds  of  potato  slop,  33  pounds  of  potatoes,  11  pounds  of 
hay,  22  pounds  of  straw,  6.5  pounds  of  bran,  plus  one  of  the  following: 

(а)  5.5  pounds  of  cotton-seed  meal,  4.4  pounds  of  rice  meal. 

(б)  5.5  pounds  of  cotton-seed  meal,  4.5  pounds  of  corn  meal. 

(c)  4.6  pounds  of  cotton-seed  meal,  9  pounds  of  molasses. 

No.  2.  Basal  ration:  132  pounds  of  potato  slop,  55  pounds  of  mangel  beets,  11  pounds 
of  hay,  22  pounds  of  straw,  66  pounds  of  bran,  plus  one  of  the  following: 

(a)  3.7  pounds  of  cotton-seed  meal,  9.9  pounds  of  rice  meal. 

( b )  3.3  pounds  of  cotton-seed  meal,  8.8  pounds  of  corn  meal. 

•  (c)  4.4  pounds  of  cotton-seed  meal,  4.4  pounds  of  molasses,  and  4.4  pounds  of  corn 
meal  or  rice  meal. 

No.  3.  Basal  ration:  132  pounds  of  potato  slop,  33  pounds  of  potatoes,  11  pounds  of 
hay,  22  pounds  of  straw,  6.6  pounds  of  bran,  plus  either  of  the  following: 

(а)  4.4  pounds  of  cotton-seed  meal,  4.4  pounds  of  rice  meal. 

(б)  3.9  pounds  of  cotton-seed  meal,  4.4  pounds  of  corn  meal. 

410 


40 


POTATO  CULLS  AS  A  SOURCE  OF  INDUSTRIAL  ALCOHOL. 


Rations  for  fattening  grown  oxen . 

Three  and  five-tenths  pounds  of  protein  and  26.5  pounds  of  starch  value  per  day 
per  2,200  pounds  live  weight. 

No.  1.  Basal  ration:  88  pounds  of  potato  slop,  88  pounds  of  forage  beets,  11  pounds 
of  hay,  26.4  pounds  of  straw,  6.6  pounds  of  bran,  plus  one  of  the  following: 

(а)  1.1  pounds  of  cotton-seed  meal,  4.4  pounds  of  rice  meal  or  corn  meal,  and  6.6 

pounds  of  molasses. 

(б)  1.6  pounds  of  cotton-seed  meal,  8.8  pounds  of  rice  meal,  and  2.2  pounds  of 

molasses. 

(c)  2.2  pounds  of  peanut  meal,  6.6  pounds  of  corn  meal. 

No.  2.  Basal  ration:  88  pounds  of  potato  slop,  55  pounds  of  potatoes,  11  pounds  of 
hay,  26.4  pounds  of  straw,  plus  either  of  the  following: 

(a)  4.4  pounds  of  cotton-seed  meal,  4.4  pounds  of  bran. 

( b )  4.4  pounds  of  peanut  meal,  4.4  pounds  of  rice  meal. 

No.  3.  Basal  ration:  132  pounds  of  potato  slop,  11  pounds  of  hay,  26.4  pounds  of 
straw,  plus  the  following:  44  pounds  of  potatoes,  5.5  pounds  of  cotton-seed  meal,  and 
3.3  pounds  of  corn  meal. 

Rations  for  dairy  cows. 

For  a  daily  milk  yield  of  22  pounds  per  1,100  pounds  of  live  weight,  there  should  be 
fed  3.8  pounds  of  digestible  proteid  and  23.1  pounds  of  starch  value  per  2,200  pounds  of 
live  weight.  The  following  rations  fulfill  these  requirements: 

(1)  66  pounds  of  potato  slop,  11  pounds  of  hay,  26.4  pounds  of  straw,  44  pounds  of 
mangel  beets,  4.4  pounds  of  cotton-seed  meal,  6.6  pounds  of  palm-nut  meal,  and  4.4 
pounds  of  bran. 

(2)  66  pounds  of  potato  slop,  11  pounds  of  hay,  26.4  pounds  of  straw,  4.4  pounds  of 
bran,  4.4  pounds  of  palm-nut  meal,  5.5  pounds  of  peanut  cake,  and  6.6  pounds  of 

molasses. 

In  order  that  other  feeding  stuffs  may  be  substituted  for  those 
given,  the  following  table  has  been  prepared,  showing  the  composition 
and  average  digestibility  of  the  feeds  mentioned: 

Percentage  composition  and  average  digestibility  of  various  feeding  stuffs. 

[From  data  compiled  by  W.  A.  Henry  .a] 


Percentage  composition. 


Per  cent  of  average  digestibility. 


Feeding  stufis. 

Water. 

Corn  meal . 

15.0 

Bran . 

11.9 

Dried  brewers’  grains . 

8.2 

Rice  meal . 

10.2 

Cotton-seed  meal . 

8.2 

Palm-nut  meal . 

10.4 

Peanut  meal . 

10.7 

Hay  (mixed  grasses) . 

15.3 

Straw  (wheat) . 

9.6 

Potato . 

78.9 

Beet  (mangel) . 

90.9 

Potato  slop . 

93.  41 

Molasses  (beet) . 

20.8 

Ash. 

Pro¬ 

tein. 

Crude 

fiber. 

Nitro¬ 

gen- 

free 

ex¬ 

tract. 

Ether 

ex¬ 

tract. 

1.4 

9.2 

1.9 

68.7 

3.8 

5.8 

15.4 

9.0 

53.9 

4.0 

3.6 

19.9 

11.0 

51.7 

5.6 

8.1 

12.0 

5.4 

51.2 

13.1 

7.2 

42.3 

5.6 

23.6 

13.1 

4.3 

16.8 

24.0 

35.0 

9.5 

4.9 

47.6 

5.1 

23.7 

8.0 

5.  5 

7.4 

27.2 

42.1 

2.5 

4.2 

3.4 

38.1 

43.4 

1.3 

1.0 

2.1 

.6 

17.3 

.1 

1.1 

1.4 

.9 

5.5 

.2 

.73 

1.97 

.55 

.34 

.04 

10.6 

9.1 

59.5 

Dry 

mat¬ 

ter. 

Pro¬ 

tein. 

Crude 

fiber. 

Nitro¬ 

gen- 

free 

ex¬ 

tract. 

Ether 

ex¬ 

tract. 

88 

60 

93 

92 

61 

79 

22 

69 

68 

62 

79 

53 

59 

91 

75 

63 

26 

86 

85 

76 

88 

32 

64 

93 

32 

71 

12 

49 

90 

61 

57 

60 

64 

53 

43 

11 

52 

38 

31 

85 

61 

90 

79 

75 

43 

91 

a  Feeds  and  Feeding,  p.  619  et  seq.  Data  credited  for  the  most  part  to  Lindsey,  Mass.  Agr.  Exp.  Sta., 
and  certain  German  authorities. 


[A  list  giving  the  titles  of  all  Farmers’  Bulletins  available  for  distribution  will  be 
sent  free  upon  application  to  any  Member  of  Congress  or  the  Secretary  of  Agriculture.] 
410 


o 


